Digitized by the Internet Archive 
in 2011 with funding from 
The Library of Congress 



http://www.archive.org/details/elementsofgeograOOsali 



GEOLOGY 

ByTHOMAS C. Chamberlin and Rollin D. Salisbury, 
Professors in the University of Chicago. (American 
Science Series.) 3 vols. 8vo. 

Vol. I. Geological Processes and Their Results. 
Vols. II and III. Earth History. (Not sold separately.) 

A COLLEGE TEXT-BOOK OF GEOLOGY 

By Thomas C. Chamberlin and Rollin D. Salisbury. 
(American Science Series.) 8vo. 

PHYSIOGRAPHY 

By R. D. Salisbury. (American Science Series.) 8vo. 
The same. Briefer Course. 12mo. 
The same. Elementary Course. 12mo. 

ELEMENTS OF GEOGRAPHY 

By Rollin D. Salisbury, Harlan H. Barrows and 
Walter S. Tower, of the Department of Geography, 
The University of Chicago. (American Science Series.) 
12mo. 

HENRY HOLT AND COMPANY, Publishers 
New York and Chicago 



AMERICAN SCIENCE SERIES. 



THE ELEMENTS OF 
GEOGRAPHY 



BY 

ROLLIN D. SALISBURY 
HARLAN H. BARROWS 

AND 

WALTER S. TOWER 

Of the Department of Geography, The University of Chicago 




NEW YORK 
HENRY HOLT AND COMPANY 



tf* 



£ 



* 



Copyright, 1912 

BY 

HENRY HOLT AND COMPANY 



STfjt Haftest'tie p«aa 

R. R. DONNELLEY & SONS COMPANY 
CHICAGO 

gC!.A319366 
7ax> i 



PREFACE 

Courses in physical geography have been given for years, with 
great success where conditions have been favorable, and with indif- 
ferent success in some other places. Recently there has been a 
widespread demand for a more general course in geography, particu- 
larly where physiography has not been thought wholly satisfactory, 
a course which should treat physiographic processes and features 
briefly, and develop at greater length the relations of earth, air, and 
water to life, and especially to human affairs. This book is designed 
to serve as the basis for such a course. The authors have sought to 
give the student (i) an understanding of the elements of geography, 
(2) an interest in the subject, and especially (3) training in clear 
thinking. Many of the facts of geography will be forgotten presently 
by most students, while the power and habit of thinking clearly Will 
be of service in meeting every problem of later years. Indeed, the 
book has been written with the belief that the chief object in 
geography teaching should be preparation for citizenship. No sub- 
ject is better adapted to this purpose. This conviction has led the 
authors to emphasize certain points now or likely soon to be of 
national importance, as, for example, the need of conserving the 
natural resources of the country. 

All rational work in general geography must be founded on physi- 
ography, and this fact has determined the organization of the mate- 
rial of this book. The principles developed have been applied at 
greatest length to the United States, because this country is of most 
interest and importance to American students. Furthermore, space 
forbade the application of these principles in detail to other countries. 

The illustrations should be regarded by the teacher as vital. 
They are intended to serve as the basis for classroom discussions and 
quizzes, and should be studied and interpreted as carefully as the 
text itself. The answers to most of the questions which appear at 
the ends of the chapters and elsewhere are not to be found in the text, 
but may be reasoned out by the student if he has read the text with 
understanding. The questions may be used for written exercises and 



VI 



PREFACE 



tests, as well as for class room discussion. In the opinion of the 
authors, these questions are by no means the least important part of 
the book, and their careful use is recommended to every teacher who 
uses the text. 

References are given at the ends of the chapters or sections, to 
assist the teacher in supplementing the work of the text. The 
extent to which these references can be used to advantage will, of 
course, depend upon the advancement of the pupils, the time at 
their disposal, and the library facilities at command. By their 
extended use, the text may be made the basis of courses more 
advanced than those of secondary schools. 

The maps at the end of the book afford the student the means of 
locating most of the places and features mentioned in the text. 



CONTENTS 



I. The Nature of Geography . . . . 

II. Earth Relations ........ 

The Solar System . . . 

The Earth as a Planet .... 

Progress of Knowledge of the Earth . 
Maps and Map Reading .... 

Terrestrial Magnetism ..... 

III. Relief Features of the Earth .... 

Relief Features of the First Order . 
Relief Features of the Second Order 
Subordinate Topographic Features 
Comparison of the Continents 

IV. The Nature and Functions of the Atmosphere . 

.General Conceptions . 

Composition ....... 

Relations of the Different Constituents to Life 

History and Future of the Atmosphere 
V. Climatic Factors: Temperature .... 

General Considerations .... 

Seasons ........ 

Relation of Temperature and Altitude 

Representation of Temperature on Maps 

Ranges of Temperature .... 

VI. Climatic Factors: Moisture .... 

Importance of Atmospheric Moisture . 

Evaporation ....... 

Humidity ....... 

Artificial Condensation .... 

VII. Climatic Factors: Pressure and Wind 

Pressure . . . . . ." . 

Representation of Pressure on Maps and Charts 

Winds ........ 

Winds and Rainfall ..... 
VIII. Storms and Weather Forecasting 

Weather Maps ...... 

Cyclones and Anticyclones .... 

Weather Forecasting ..... 

Local Storms ..... 
IX. Tropical Climate . . . . . 

Distribution ....... 

General Characteristics of Tropical Climates 

Types of Climate Within the Tropics . 

The Future of the Tropics . ... 
vii 



3 

7 

7 

io 

22 

24 

2 9 

33 
33 
36 
40 
40 
44 
44 
46 

47 

52 

55 

55 

64 

67 

70 

78 

84 

84 

85 

89 

99 

102 

102 

104 

in 

118 

126 

126 

130 

142 

147 

154 

154 

156 

159 

176 



viii CONTENTS 

X. Types of Climate in the Temperate (Intermediate) Zones 178 
Areas Affected . . . . . . . .178 

General Characteristics of Climates of the Temperate 
Zones ........ 

Types of Climate ...... 

XL Climate of Polar Regions ...... 

General Considerations .... 

The Antarctic Region . . 

The Arctic Regions ...... 

XII. The Oceans 

General Considerations ..... 

Temperature of the Sea ..... 
Movements of Sea-water ..... 
The Life of the Sea . . . . 

XIII. The Materials of the Land and Their Uses 

General Constitution ...... 

Soils . . ' 

Mineral Products and Their Uses 
Conservation of Mineral Resources 

XIV. Changes of the Earth's Surface Due to Internal Forces 

Slow Crustal Movements ..... 

Earthquakes ........ 

Vulcanism ........ 

XV. Modification of Land Surfaces by External Agents 

The Work of the Wind ...... 

Ground-water ....... 

The Work of Streams ...... 

The Work of Ice ....... 

XVI. The Uses and Problems of Inland Waters . . . 

Navigation ........ 

Water Power . . . . . 

Irrigation ........ 

Reclamation of Swamp and Overflowed Lands 

Water Supply ....... 

XVII. Mountains and Plateaus and Their Relations to Life 

Mountains . . . . . . ' . 

Plateaus ........ 

XVIII. Plains and Their Relations to Life .... 

Life in Well-watered Plains of Middle Latitudes 

Life in Semi-arid Plains ..... 

Life in Arid Plains ...... 

Life in Arctic Plains ... . 

Life in Humid Plains of Low Latitudes 
XIX. Coast-lines and Harbors ...... 

XX. Distribution and Development of the Leading Industries 
of the United States ..... 

Agriculture ........ 

Forest Resources and Lumbering 

The Fishing Industries ...... 

Mining, Quarrying, Etc. .... 

Manufacturing Industries ..... 
XXL Distribution of Population; Development of Cities 

Factors Affecting Density 

Cities ......... 



LIST OF PLATES 

AT END OF VOLUME 

Plate I. North America 

Plate II. United States 

Plate III. South America 

Plate IV. Europe 

Plate V. Asia 

Plate VI. Africa 

Plate VII. Australia 



ELEMENTS OF GEOGRAPHY 



CHAPTER I 
THE NATURE OF GEOGRAPHY 

Ancient and modern geography. Geography has been studied 
since ancient times, for people always have wanted to know about 
the earth on which they lived; but the conception of geography has 
changed greatly as years have gone by. In olden times geography 
was regarded as a description of the earth. It included an account 
of the countries into which the earth is divided, their physical features, 
such as rivers, mountains, and plains, and their inhabitants and pro- 
ducts. Modern geography is concerned especially with the effects 
of physical features, such as land forms, water, and climate, on living 
things. Hence geography is defined now as the study of the earth 
in its relations to life. 

Divisions of geography. It is clear that there are two main 
parts to the study of geography: (i) The physical features of the 
earth (land, water, air) which affect life; and (2) the ways in which 
different forms of life respond to their physical surroundings. 

Various groups of physical phenomena may be the subjects of 
special study. Thus the phenomena of the atmosphere are considered 
in meteorology and climatology; those of the waters in oceanography 
and hydrography; and those of the lands in physiography, as some would 
define that term. Similarly, earth relations to life may be studied 
with special reference to plants {plant- or phy to- geography) , to ani- 
mals (animal- or zoo-geography), or to man (human- or anthropo- 
geography) . 

Relations to other subjects. The study of these different 
phases of geography brings it into contact with many other sciences. 
The form, size, and motions of the earth are matters of astronomy 
as well as geography; the origin and characteristics of land forms 

3 



4 ELEMENTS OF GEOGRAPHY 

and the distribution of useful minerals are matters of geology as well 
as geography; the effects of physical conditions on plant and animal 
life are phases of botany and zoology as well as geography; the distri- 
bution of mankind, man's subdivision of the earth into political 
units, and many other matters, relate geography closely to history; 
and man's present activities, influenced by geographic conditions, 
are factors of political economy. 

Importance of human geography. Since man is the most 
important form of life, most interest attaches to the study of the 
earth in its relations to- him. Human activities are so many and 
varied, and are influenced in so many ways by physical conditions, 
that special study often is made of related effects. Thus economic 
geography traces the influence of natural factors in the production 
of things useful to man. The relations of land forms, soil, and 
climate to the raising of crops is an example. Commercial geography 
considers the influence of natural factors in the transportation and 
exchange of various commodities, as the trade in tropical fruits between 
warm regions and those too cold to raise them. Historical geography 
is concerned with the influence of physical conditions on past events. 
Political geography traces the influences of location, topography, 
climate, and natural resources on the development of different coun- 
tries. The effect of position may be seen in the fact that the Nether- 
lands, at the mouth of the Rhine, rose to great commercial importance, 
in contrast with agricultural Denmark on the one side, and industrial 
Belgium on the other. 

The basis of other studies. Since geography shows the many 
ways in which the earth is related to the life of man, it is important 
as the basis of many other studies. 

Geography is especially important in connection with the study 
of history, for in all ages the conditions under which people lived 
have influenced their occupations, their stage of development, and 
their relations to the rest of the world. The better geography is 
understood, therefore, the easier it is to understand the significance 
of historical events. The Jews in Palestine never developed sea- 
faring habits because the nearest coast was devoid of good harbors, 
while their neighbors, the Phoenicians, on a more favorable coast, 
were the first good sailors, and for many years were influential in 
Mediterranean districts outside their own country. Russia has 
striven for more than two centuries to secure satisfactory seacoasts, 
and as a result has been led to great territorial expansion and into 



THE NATURE OF GEOGRAPHY 5 

wars with her neighbors. Most of the incidents which led up to the 
war with Japan were connected with this expansion. Great Britain, 
protected from invasion by her insular position, was able at an early 
date to use her natural resources to great advantage, and became the 
leading manufacturing and commercial nation of the world. In 
our country, slavery developed most extensively in the South, mainly 
because the conditions of field labor there favored it more than in 
the North. These few examples suggest the close connection between 
geography and some important facts and phases of history. 

Geography is related no less intimately to present events. The 
distribution of people over the face of the earth, the manner in which 
they live, and their grouping in countries and cities always bear some 
relation to earth conditions. Many old cities, like Venice, were 
located where defense against invasion was easy. Most recent 
cities have been located with respect to natural advantages for manu- 
facturing or commerce. Food, dress, shelter, occupations, industries, 
products, trade, and many other facts and conditions of life are 
influenced by physical surroundings. Deserts are characterized 
by scanty vegetation, mostly unlike that of other regions. Desert 
animals also are few because plants are few and water scarce, and 
they differ from those of well-watered regions, partly because of 
the difference in the plants on which they must feed. Since man 
depends on plants and animals for food, clothing,. and shelter, desert 
populations are small. 

Tropical natives wear little clothing and eat little meat, largely 
because bodily temperatures are maintained easily without either. 
They engage but little in commerce, because their wants are few. 
The people of middle latitudes, on the other hand, must adapt them- 
selves, in the matter of food, clothing, and shelter, to extremes of 
heat and cold. Their wants are therefore many and varied. Com- 
plex industries and world commerce are needed to satisfy them. 
The United States is the greatest producer of foodstuffs, because of 
the great extent of favorable surface, soil, and climate — resources 
which a progressive people have used to advantage. Several coun- 
tries of western Europe have advantages for extensive manufacturing, 
such as supplies of coal near good seaports; but they cannot produce 
all the raw materials needed for their factories, nor all the food for 
their factory workers. Hence large quantities of raw materials and 
food, like cotton and copper, flour and meat, are exported annually 
from the United States to these European countries. Great Britain, 



6 ELEMENTS OF GEOGRAPHY 

being a small but highly developed country, requiring many things 
from abroad, has been led to abolish nearly all import duties. The 
United States, on the other hand, is so nearly self-sufficient in most 
necessities of life, that it has been led to maintain rather high im- 
port duties, with a view to insuring the home producer an advantage 
m supplying local markets. Not all parts of the United States, 
however, are agreed on the subject of import duties (tariff), for the 
country is so large that its several parts differ in geographic conditions, 
and hence in leading interests. Many Minnesota farmers, for example, 
oppose reciprocity with Canada because they fear lower prices for 
their grain and live stock if Canadian grain and cattle come in free. 
Most of the people of Massachusetts, on the contrary, interested 
primarily in manufacturing, favor such a treaty because it may open 
a better market for their manufactured wares and give them cheaper 
food-stuffs. Thus some of our current politics is, at bottom, a matter 
of sectional geography. 

An understanding of the larger relations between physical con- 
ditions and life in general is necessary to an understanding of the 
effects of the physical surroundings of man on his interests and 
activities. This in turn helps one to understand the affairs of the 
world, and therefore is important to good citizenship. 



CHAPTER II 
EARTH RELATIONS 

The Solar System 

Early conceptions of the relations of the earth. For thou- 
sands of years men believed that the earth was the center of the 
universe. They thought that the sun, moon, and other heavenly 
bodies actually revolved around it (as they seem to), and that these 
bodies were created and maintained to give light and heat to the 
inhabitants of the earth. In the sixteenth century it was proved 
that the sun, moon, and stars appear to revolve about the earth 
because the latter rotates on an axis, and that, far from being the 
central and largest part of the universe, the earth is merely one of 
the smallest of a great family of bodies. Beyond the great system 
to which the earth belongs, there are many thousands of stars, each 
of which may be compared to our sun, though many of them are 
vastly larger. 

Members of solar system. The solar system includes the sun 
and all the bodies which revolve about it (Fig. i). There are eight 




Fig. i. Diagram of the solar system. The size of the bodies is exaggerated 
enormously as compared to that of the orbits. 

planets, of which the earth is one. To us, all the planets except our 
own appear as stars, but in their motions they differ from other 
stars. Commencing with the nearest to the sun, the planets are, 
in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, 
and Neptune. All but Mercury and Venus have satellites correspond- 
ing to our moon. Saturn has nine of them. 

7 



8 ELEMENTS OF GEOGRAPHY 

Besides the planets and their satellites, the solar system includes 
numerous (more than 400) asteroids, bodies much smaller than the 
planets, intermediate in position between Mars and Jupiter, and 
those comets which revolve about the sun. Comets and asteroids 
have little influence on the earth. 

The sun is a vast sphere (more than 1,000,000 times as large as 
the earth) and very hot. From the sun the earth receives nearly all 
its heat and light. The other planets shine only by reflected sunlight. 

The planets. The planets are all of similar form, and probably 
of similar composition. All rotate on axes, and move in nearly cir- 
cular paths about the sun in the same direction, but they are strik- 
ingly unlike in some respects. Jupiter, the largest, has a diameter 
more than ten times as long as that of the earth, while Mercury, 
the smallest planet, has a diameter only about one-third that of the 
earth. The innermost planet revolves about the sun in 88 days, 
the outermost in 165 years. The former is about two-fifths as far 
from the sun as the earth is, while the latter is over 30 times as dis- 
tant. The shortest rotation period of a planet is less than 10 hours, 
while that of Venus is nearly 225 days. From the standpoint of 
life, the earth is the most favored of the planets in all these respects, 
Indeed, the conditions of heat and light would prevent the existence 
of such life as we know on most of the other planets. 

The origin of the earth. The history of the earth's origin 
is not known with certainty. Until the close of the last century, 
Laplace's nebular hypothesis of the solar system had been accepted 
with little question. This hypothesis assumed that the sun, together 
with all other members of the solar system, were once parts of a glow- 
ing-hot gaseous mass, called a nebula. It assumed further, that this 
enormous volume of gas was rotating and cooling. Rotation caused 
its equatorial part to bulge, cooling caused the whole to shrink, and 
shrinking quickened rotation. The result, so the theory runs, was 
that the main body of the rotating mass shrank away from the equa- 
torial bulge, leaving it outside as a ring, somewhat like the rings which 
surround Saturn now. Once left outside, the ring was assumed to 
have broken up, and its materials to have come together into a sphere, 
making a planet. The eight planets were assumed to have been 
formed from eight successive rings, the outermost being the oldest. 
The sun is the part of the original mass not made into planets. Some 
of the planets in turn developed rings in the same way as the central 
body, and these rings became satellites. 



EARTH RELATIONS 9 

According to this hypothesis, the earth, at its birth, was a huge 
ring of hot gas, from which the central body, including what is now 
the sun and the two planets nearest to it, shrank away. The sub- 
stance of this ring became a spheroidal mass, which, as it rotated, 
gave off a ring that became the moon. By cooling, the gases of 
the early earth condensed into liquid, and still later, according to 
the hypothesis, the cooler outer part became solid. In applying the 




Fig. 2. Spiral nebula. (Photographed at Yerkes Observatory.) 



hypothesis to the earth, it was long assumed that the interior of the 
earth was still liquid; but this is not a necessary part of the nebular 
hypothesis. 

In recent years strong arguments have been brought against this 
hypothesis, — arguments so strong that, in its original simple form 
at least, the nebular hypothesis can be held no longer. 

Another hypothesis, known as the planetesimal hypothesis, has 
been suggested in its place. This hypothesis assumes that the 
beginning of the solar system was a spiral nebula, similar to the 
commonest type of existing nebulas (Fig. 2). This nebula is assumed 



io ELEMENTS OF GEOGRAPHY 

to have consisted, like nebulae now, of a central portion, with two. 
long curved arms. Like existing spiral nebulae, too, it is assumed to 
have been composed of multitudes of small solid bodies, not hot, 
together with numerous particles of gas. Each small body is thought 
to have revolved about the center of gravity of the whole. The 
development of the solar system out of this nebula consisted in the 
gathering of these small, scattered bodies into a few; namely, the sun, 
the planets and their satellites, and the asteroids. According to this 
hypothesis, the earth was never gaseous, never liquid, and perhaps 
never very hot on the outside, but grew to its present size by the 
accumulation of multitudes of small bodies. Its interior heat was 
developed during its growth, the central parts being squeezed into 
smaller space by the weight of all matter added to the outside. 
This process produced heat. The amount of heat developed in 
this way would be quite enough to explain the temperature of the 
earth's interior. 

The nebular hypothesis assumed that the atmosphere was once 
enormously more extensive than now, that it has become less and 
less, and that it will in time disappear altogether. The planetesimal 
hypothesis assumes that the earth, in the early stages of its growth, 
had little or no atmosphere, that the atmosphere has grown with 
the rest of the earth, and that there is no reason to suppose that it 
is becoming less now, or that it will become less in the future. 

No serious arguments have been brought against the planetesi- 
mal hypothesis, and it is, at the present time, the most acceptable 
hypothesis of the earth's origin. 

The Earth as a Planet 

Form. The form of the earth is very much like that of a sphere, 
but since it is not exactly a sphere, it is called a spheroid. The form 
has been determined in various ways: (i) Ships have sailed around 
it. This proves that it is everywhere bounded by curved surfaces, 
but it does not prove that it is a sphere or even a spheroid, for it would 
be possible to sail around it if it had the shape of an egg. (2) 
When a vessel goes to sea, its lower part disappears first, and when 
a vessel approaches land, its highest part is seen first from the land. 
By people on the vessel, the highest lands are seen first, and the low 
ones later; the spires and chimneys of buildings appear before the 
roofs, and the roofs before the. lower parts. Like (1) above, these 



EARTH RELATIONS n 

facts show only that the earth has a curved surface. But from 
whatever port vessels start, and in whatever direction th y sail, 
objects on land disappear at about the same rate. This means that 
the curvature of the surface is nearly the same in all directions. A body 
whose curvature is the same in all directions is a sphere, and a body 
whose curvature is nearly the same in all directions is nearly a sphere 
This is the condition of the earth. (3) Again, the earth sometimes 
gets between the sun and the moon. It then casts a shadow on the 
moon (making an eclipse), and this shadow always appears to be 
circular. In these and other ways it is known that the form of the 
earth does not depart greatly from that of a sphere. (4) That the 
earth is not exactly round, however, is shown in various ways. For 
example, a body weighs slightly more in high latitudes than in low 
latitudes. This means that it is nearer the center of the earth in 
the high latitudes than in the low; or, in other words, that the earth 
is, not a true sphere. (5) Again, as one travels in any direction, new 
stars appear above the horizon ahead, and rise in the sky as the 
traveler advances, while those which were low in the sky behind, 
sink and disappear below the horizon. This indicates that the 
surface of the earth is curved. The distance of the stars is ^o 
great that, were the surface of the earth flat, a given star would 
appear to be at the same elevation above the horizon at all places 
on the earth. Were the surface equally curved everywhere, the 
same distance would have to be traveled in all parts of the earth 
in order to change the altitude of stars by a given amount. It has 
been found, however, that for a given amount of change, one must 
travel farther in high latitudes than near the equator. Like the 
variation in the weight of a body, this shows that the earth is a 
spheroid, rather than a true sphere. 

Origin and consequences of the earth's form. There is no 
reason for thinking that the form of the earth was ever very different 
from its present form. Even if it had been very irregular originally, 
this form could not have persisted long, for the rocks of the deep 
interior would have yielded under the very unequal pressures 
that would have existed beneath the high places and the low ones. 
The higher parts of the surface would have sunk, and the lower parts 
would have been forced outward, until a roundish form was developed. 
Again, as the surface rocks decayed and broke up, rains and streams 
would have washed the loose material from the high places to the 
low ones, helping to produce a spherical shape. 



12 ELEMENTS OF GEOGRAPHY 

The spheroidal form of the earth facilitates travel and trans- 
portation. It aids commerce in another important way. The attrac- 
tion of the earth causes bodies to have weight. Because the earth 
is nearly round, gravity is nearly equal everywhere upon its sur- 
face, and, as we have already seen, the weight of a given object 
is therefore nearly constant. If the weight of things varied greatly 
from place to place, this variation would interfere seriously with 
trade between different parts of the world. 

Size. The circumference of the earth is nearly 25,000 miles, 
and its diameter nearly 8,000 miles. Since the earth is not a perfect 
sphere, its various diameters and circumferences are not exactly 
equal. Its longest diameter is 7,926.5 miles and its shortest nearly 
27 miles less (7,899.7 miles). 

The area of the earth's surface is nearly 197,000,000 square 
miles. Were the earth as large as some other planets, intercourse 
between the opposite sides would be much more difficult than now. 
Thus, the proportions of Jupiter applied to the earth would mean 
a width of 30,000 miles for the continent of North America, and an 
expanse of water between the United States and Europe which only 
the fastest steamships could cross in less than six weeks. The 
amount of fuel required for such long ocean voyages would seriously 
restiict intercourse between different parts of the world. As it is, 
modern means of transportation make it possible for every nation 
to draw supplies from the most remote regions. 

Motions 

The earth has two principal motions: (1) It rotates on its shortest 
diameter, called its axis, and (2) it revolves around the sun. The 
axis is an imaginary line, and its ends are the poles. The circumfer- 
ence midway between the poles is the equator. 

Rotation. The rotation of the earth from west to east gives us 
day and night, for one side of the earth and then the other is turned 
toward the sun during each rotation. The time of rotation, about 
24 hours, determines the length of a day (day and night). The 
length of the period of rotation can be measured by means of the 
stars (How?). The period of rotation thus measured is called the 
sidereal day (Latin sidus = a, star). The time between two successive 
noons is the apparent solar day. As the earth rotates on its axis, it 
,also moves forward in its path around the sun, faster when nearer 
the sun, and slower when farther away from it. One result of this 



EARTH RELATIONS 



13 



forward motion of the earth is to make solar days a little longer than 
sidereal days (Why?) . Solar days vary slightly in length (Why?) . The 
mean solar day has the average length of the apparent solar days. 

Human activities are in general adjusted to the turning of the 
earth, the succession of daylight and darkness affording convenient 
intervals for work and rest. In those parts of the earth where the 
intervals of light and of darkness are many days (instead of hours), 
this habit of regularity of work and rest is less general. During 
the long period of light, the hunting people of Greenland, for example, 
cease their work or seek rest only when fatigue overtakes them. 
During the long night they have no regular work or exercise, and 
are much less vigorous than in the period of light. The long night 
of polar regions is very trying to the health and strength of people 
accustomed to a period of light each day. 

The period of rotation furnishes also a natural unit for measuring 
time. Astronomers use the sidereal day as a time unit, but the mean 
solar day is the one commonly used. Again, the rising and setting 
of the sun, due to the earth's rotation, give us a simple system of 
directions. 

Revolution. The earth revolves about the sun in a little more 
than 365 days, and the period of revolution fixes the length of the year. 
The path of the earth around the sun is its orbit. The orbit of the 
earth is not a circle, but a curve called an ellipse (Fig. 3), and the 



Perihelion 




Aphelion 



Fig. 3. The orbit of the earth is an ellipse, with the sun in one of the foci. 



distance of the earth from the sun varies from time to time. When 
the earth is nearest the sun {perihelion), the distance between them 
is about 3,000,000 miles less than when they are farthest apart 
{aphelion). The earth is nearest (about 91,500,000 miles) the 
in the early par*: of the winter; of the northern hemisphere (about 



14 



ELEMENTS OF GEOGRAPHY 



January ist), and farthest (about 94,500,000 miles) from it early in 
the summer. 

The motion of the earth through space during its revolution 
about the sun is at the rate of about 600,000,000 miles a year, or more 
than 1,100 miles each minute. 

The earth's axis is inclined toward the plane of its orbit about 
23^ degrees (Fig. 4). This position of the axis, together with 





S'/i\\f^ 




Fig. 4. Diagram showing the position of the earth with reference to the sun 
at the solstices and equinoxes, and the inclination of its axis. 



the motions of the earth, has much to do with the distribution of 
the heat and light received from the sun, with the changes in the 
length of day (daylight) and night, and with the seasons. 

Latitude, Longitude, and Time 

Latitude. The equator has been defined as the circle about 
the earth midway between the poles. Circles parallel to the equa- 
tor are parallels. The number of parallels which might be drawn 
is very large, though only a few are represented on maps. The 
length of parallels varies greatly, those near the equator being longer, 
and those near the poles shorter. The north and south lines that 
pass from pole to pole on the earth's surface are meridians. All 
n~eridians come together at each pole. 

A few meridians and parallels appear in Fig. 5, which shows 



1 



EARTH RELATIONS 15 

the earth in two positions. The left-hand part of the figure shows 
the half of each parallel represented and the whole of each meridian. 
The right-hand part shows the relation of parallels to the North 
Pole. The distance between the equator and either pole is divided 





Fig. 5. Parallels and meridians. 

into 90 parts, called degrees (written oo°). Each degree is divided 
into 60 parts, called minutes (6o'). Each minute is divided into 
60 parts, called seconds (60") • Distance north or south of the equa- 
tor may therefore be determined from a globe or map by means of 
parallels. The 'system of parallels and meridians is made possible 
by the form of the earth and its rotation on its axis. 

Distance north or south of the equator is called latitude. North 
latitude is north of the equator, and south latitude is south of it. The 
degrees, minutes, etc., are numbered from the equator toward the 
poles. The latitude of the equator is o°. Latitude i° N. is one 
degree north of the equator, and latitude oo° N. is at the North Pole. 
Latitude i° S. is one degree south of the equator, and latitude go° 
S. is at the South Pole. If the latitude of a place is 40 40' 40" N., 
its distance and its direction from the equator are accurately known; 
but its position on the parallel of 40 40' 40" is not known, for that 
parallel runs around the earth. 

Longitude. Position on a parallel is indicated by means of the 
meridians which cross it. The number of possible meridians is very 
great, but, as in the case of parallels, only a few are commonly shown 
on maps. One meridian, that passing through Greenwich, England, 
where the British Royal Observatory was established in 1675, is 
usually chosen as the meridian from which distances east and west 
are reckoned (Fig. 6). This meridian is the meridian of o°, and is 
sometimes called the prime meridian. Distance east or west of this 



i6 



ELEMENTS OF GEOGRAPHY 




meridian is known as longitude. Places east of longitude o° are in 
east longitude, and those west of it are in west longitude. East and 
west longitude respectively are regarded as extending 180 from the 

meridian of o° ; that is, half-way 
around the earth. 

The position of a place on 
the earth's surface may be fixed 
exactly by means of meridians 
and parallels. If a place is in 
longitude 3o°E.,its distance east 
of the meridian o° is known. If 
at the same time it is in latitude 
30 N., it must be on the paral- 
lel of 30 N. where it is crossed 
by the meridian of 30 E. So 
convenient and accurate is this 
method of locating places and 
reckoning distance that parallels 
and meridians are used in many 
places as boundaries between 
states, counties, and townships. 
They have great value, too, in 
determining positions at sea. 
The modern science of navigation, so important to commerce, may 
almost be said to have had its foundation in the discovery of these 
earth relations. 

The poles are the only places which have latitude but no longitude. 
Since all meridians come together at the poles, the poles cannot be 
said to lie either east or west of the meridian of Greenwich. At the 
North Pole the only direction is south, and at the South Pole the only 
direction is north. 

Longitude and time. There is a definite relation between 
longitude and time. Since the earth turns through 360 in 24 hours, 
it turns 15 in one hour, and 15' of longitude in one minute of time. 
The sun therefore rises one hour earlier at a place in longitude o° 
than in a place in the same latitude in longitude 15 W., and one 
hour later than at a place in the same latitude in longitude 15 E. 
Similarly, noon comes an hour earlier in longitude o° than in longitude 
1 5° W., and an hour later than in longitude 15 E. All places on a 
given meridian have noon at the same time and midnight at the same 



Fig. 6. Diagram showing the position 
of the axis of the earth, the poles, the 
equator, the meridian of Greenwich, and 
the meridian of 180 . 



EARTH RELATIONS 



i7 



time, and such places are said to have the same time; but places on dif- 
ferent meridians have different times. St. Louis is about 15 farther 
west than Philadelphia, and Denver is about 15 west of St. Louis. 
When it is noon at Philadelphia it is about eleven o'clock at St. Louis 
and ten at Denver. When it is one o'clock at Philadelphia it is noon 
at St. Louis and eleven o'clock at Denver, and when it is noon at 
Denver it is one o'clock at St. Louis and two at Philadelphia. 

The variations of time with changes of longitude become apparent 
when long journeys are made either east or west. Thus a watch which 




Fig. 7. Map showing standard time belts of the United States. 



has the correct time in New York has not the correct time when it is 
carried to Chicago. To avoid the difficulties of time-keeping growing 
out of travel, the railroads of the United States have adopted a sys- 
tem of standard time. Under this system the country is divided into 
north-south belts of convenient width (Fig. 7), and in each belt all 
railways use the same time. The railway time in adjacent belts 
differs by one hour. By this system, clocks and watches do not show 
correct local time except on one meridian of each belt. The irregular 
boundaries of the belts are due to the adoption of the nearest import- 
ant railway points as the places for changing time on east and west 
journeys. 



18 ELEMENTS OF GEOGRAPHY 

Lengths of degrees. The length of a degree of longitude, as 
measured on the surface of the earth, is the 315-7 part of a parallel. 
Since the parallels are very much shorter near the poles than near 
the equator, the length of a degree of longitude is less in high than in 
low latitudes. At the poles, where the length of the parallel becomes 
zero, the length of a degree of longitude also becomes zero. At the 
equator, the length of a degree of longitude is a little more than 69 
(69.16) miles. 

The most important result of variation in the lengths of degrees 
of longitude is found in the routes followed by vessels on long voyages 
east and west. The shortest route {the Great Circle route) between 
two points lying in about the same latitude, as San Francisco and 
Yokohama, is not along the parallel of 36 N., but is a route which 
takes the vessel several degrees north of 36 in the mid-Pacific. 
This can be seen readily on a globe. Another result appears when 
we attempt to show the curved surface of the earth on a flat map 
(P- 25). 

Degrees of latitude are measured on meridians. They also vary 
in length. The length of a degree of latitude is' about 68^ miles 
in India, while in Sweden, the most northerly place where a degree 
has been measured, it is 69^ miles. All measurements which have 
been made show that the length of a degree of latitude, measured 
on the earth's surface, increases as the poles are approached. At 
the poles it is calculated that it must be about 69^ miles. In the 
United States, the average length is about 69 miles. The increase 
of length of the degree toward the poles means that the earth is 
flattened there. 

Inclination of Axis and its Effects 
The sun's rays illuminate one-half of the earth all the time. 
The border of the illuminated half is called the circle of illumina- 
tion (Fig. 8). All places on one side of the circle of illumination have 
day, while all places on the other side have night. If the axis about 
which the earth rotates were perpendicular to the plane in which 
the earth revolves about the sun, the circle of illumination would 
always pass through the poles. Under these conditions, half of the 
equator and half of every parallel of latitude would be illuminated 
all the time, as in Fig. 8. If the half of each parallel were always 
illuminated, the days and nights would be equal everywhere, for it 
takes just as long for a place at A (Fig. 8) to move to B (six hours, 



EARTH RELATIONS 



19 




half of a twelve-hour day) as fpr it to move from B to A' (half of a 
twelve-hour night) . Since days and nights are not equal at all sea- 
sons in most parts of the earth, it proves that the axis on which 
the earth rotates is not per- 
pendicular to the plane of its 
orbit. 

Again, if the earth rotated 
on an axis perpendicular to 
the plane of its orbit, the sun 
would always be equally high 
at any given place at the same 
hour of the day. But this is 
not the case. In the United 
States, for. example, the sun 
is much higher above the 
horizon at noon in summer 
than in winter. The same is 
true in all latitudes similar to 
those of the United States. 

This variation of the angle 
at which the sun's rays strike 
the same place at different 
times, as well as the unequal 
. lengths of days and nights in most places, is the result of the inclination 
of the axis on which the earth rotates as it revolves around the sun 
(Fig. 4) . The position of the axis is constant throughout the year. The 
effect of the inclination of the axis is illustrated by Fig. 4, which rep- 
resents the earth in four positions in its orbit. In the position marked 
March 21st, the half of each parallel (the half toward the reader) is 
illuminated. At this time, therefore, days and nights are equal 
everywhere. In the position marked June 21st, more than half 
(the part not shaded) of every parallel of the northern hemisphere is 
illuminated, and there the days are more than 12 hours long and the 
nights correspondingly less. In the southern hemisphere the nights 
are longer than the days. In the third position, September 2 2d, the 
days and nights are again equal everywhere, for the circle of illumina- 
tion divides every parallel into two equal parts. In the figure, the 
lighted part is away from the reader. In the fourth position, Decem- 
ber 2 2d, more than half of each parallel in the southern hemisphere 
is in the light, and there the days are longer than the nights, while 



90° 



Fig. 8. Diagram to illustrate the fact that 
half of the earth is lighted by the sun at any 
one time. The parallel lines at the right 
show the direction of the sun's rays. The 
part of the earth not shaded is lighted by 
the sun; the other half is in darkness. The 
line between the illuminated half and the 
half which is not illuminated is the circle of 
illumination. This diagram represents con- 
ditions at the time of an equinox. 



20 



ELEMENTS OF jEOGRAPHY 



in the northern hemisphere the nights are longer than the days. 
Twice during the year, therefore, on March 21st and September 
2 2d, the days and nights are equal everywhere. These times are 

known as the equinoxes. 
The equinox in March is 
the vernal equinox; that 
in September is the autum- 
nal equinox. 

When the earth is in 
the relation to the sun 
shown in the position 
marked June 21st, Fig. 4, 
the days are longest in the 
northern hemisphere, 
the sun is highest in the 
heavens at noon, and its 
rays fall perpendicularly 
on the surface of the earth 
farther north (23 27'+) 
than at any other time. 
This is the summer solstice 
(Fig. 9). The winter sol- 
stice occurs six months 
later, when the sun's rays 
strike the earth vertically 
2 3^2° (nearly) south of the 
equator (Fig. 10), and 
when the days of the 
southern hemisphere are 
longest and those of the 
northern shortest. Figs. 
9 and 10 also show that 
the days and nights, are 
always equal at the equator, 
since the equator is always 
bisected by the circle of 
illumination. Days and 
nights are not always 
equal in any other lati- 
tude, unless at the poles, 




Fig. 9. Diagram illustrating the effect of 
inclination of the earth's axis on the length of 
day and night. In the figure, more than half 
of every parallel of the northern hemisphere is 
illuminated. The days in the northern hemi- 
sphere are therefore more than twelve hours 
long, since the half of each parallel is the meas- 
ure of 180 of longitude, and 180 of longitude 
corresponds to twelve hours of time. Similarly 
less than half of every parallel of the southern 
hemisphere is illuminated, and the days are 
therefore less than twelve hours long. 

Fig. 10. The relation of the earth to the 
sun's rays at a time six months later than that 
represented in Fig. 9. The conditions of day 
and night in the hemispheres are reversed. 



EARTH RELATIONS 



21 



where there is one day (or period) of six months of light, and one 
night (or period) of six months of darkness. 

The relative duration of daylight and darkness, and the angle 
at which the sun's rays strike the earth, are the chief causes of changes 
of seasons. Thus at the equator, where the hours of day and night 
are always equal, and the sun's rays nearly vertical at all times of 
the year, seasons change but little, while toward the poles, say in 
Lat. 6o°, where days and nights are very unequal most of the time, 
seasons are very much more extreme. 

It will be seen, therefore, that most of our methods of reckoning 
years, seasons, days, distances and positions, weights, and directions 
depend on the various earth relations. 

Apparent motion of the sun. The effect of the inclination of 
the axis of the earth is to make the sun appear to move north and south 
once during each revolution of the earth about the sun. That is, 
the revolution of the earth 
about the sun while it ro- 
tates on an inclined axis, 
makes the sun appear to 
move from a place where 
its rays are vertical 23^° 
(nearly) north of the equa- 
tor (direction S, Fig. n), 
to a place where they are 
vertical 23^° (nearly) 
south of the equator (direc- 
tion W), and back again, 
in one year. The result, so 
far as the earth is con- 
cerned, is as if the sun 

moved from S, which corresponds to the time of the summer solstice, 
to Sp & A, which corresponds to the time of the autumn equinox, 
then to W, which corresponds to the time of the winter solstice, 
then back again to Sp &° A, which corresponds to the spring equi- 
nox, and finally to S, while the earth is making one circuit about 
the sun. 

When the sun is vertical at points north of the equator, the days 
are longer than the nights in the northern hemisphere, and the sun's 
rays strike the surface in the northern hemisphere more nearly ver- 
tically than they do in the southern hemisphere. The greater number 




Sp&A 



Fig. 11. Diagram illustrating the appar- 
ent motion of the sun. 



22 



ELEMENTS OF GEOGRAPHY 



of hours of sunshine and the more nearly vertical rays explain the 
warmth of our summer, even though the earth is then farthest from 
the sun. In high latitudes, as in western Canada, the long period of 
sunlight (16 to 18 hours) is an important factor in the successful 
cultivation of crops, in spite of the short summer. When the sun is 
vertical at the equator, days and nights are equal everywhere, and 
when the sun is vertical south of the equator, days are longer than 
nights in the southern hemisphere, and the sun's rays are more nearly 
vertical there than in the northern hemisphere. 

The northernmost parallel where the sun's rays are ever vertical 
is called the tropic of Cancer. The corresponding southernmost 
parallel is the tropic of Capricorn. The tropics are nearly 23^2° 
(23 27'+) from the equator, because the axis of the earth is inclined by 
that amount toward the plane of its orbit. The sun is vertical at the 
tropic of Cancer at the time of the summer solstice, and at the tropic 
of Capricorn at the time of the winter solstice. The parallels just 
touched by the circle of illumination at the time of the solstices are 
the polar circles. They are as far from the poles as the tropics are 
from the equator. They are therefore in latitude about 66j^°. 
The one in north latitude is the Arctic circle, and the one in south 
latitude is the Antarctic circle. 

Within the polar circles the differences of the seasons are chiefly 
a matter of daylight and darkness. Between the tropics there are 
no seasons like those of the United States. Hence it is only between 
the polar circles and the tropics that there are four seasons of the 
year, to be called truly spring, summer, autumn, and winter. 




Fig. 12. The world accord- 
ing to Hecataeus, 500 b. c. 
Shaded areas = water. 



Progress of Knowledge of the Earth 

The lands bordering the Mediterra- 
nean Sea were the first center from 
which effective geographical exploration 
was undertaken. Very ancient civiliza- 
tions grew up in the rich valleys of the 
Euphrates, Ganges, and various Chinese 
rivers, but the explorations carried on 
from those centers added little to the 
knowledge of the earth. The ancient 
Greeks thought the world was a flat disc, 
bordered by an ocean river (Fig. 12). 



EARTH RELATIONS 



23 




Fig. 13. The known world according to 
Ptolemy, 150 A. d. Shaded areas = land. 



The spherical shape of the earth was first proved by Aristotle in the 
fourth century B. C, and its size was first determined approximately 
in the next century by Eratosthenes, another Greek philosopher. 
During the fourth century B. C, Grecian sailors explored the western 
coast of Europe and dis- 
covered Great Britain, 
and Alexander the Great 
added much to the pre- 
vious knowledge of Asia 
as far east as India. 

During most of the 
Middle Ages little prog- 
ress was made. Indeed, 
what was known of the 
world by Ptolemy in the 
second century A.D. (Fig. 
13) represented almost the 
sum total of geographic 

knowledge to the middle of the thirteenth century. The book of Marco 
Polo (1298), describing his travels through Asia and the neighboring 
islands, furnished Europe with much of its early information con- 
cerning the East; but the influence of this great work was not felt 
at once. The printing press had not been invented, geography was 
clogged by tradition, and much of the account appeared to be a 
collection of romantic tales rather than of facts. Later, the views 
of no less an explorer than Columbus were influenced greatly by the 
work of Marco Polo. 

From early times there was an important trade between Europe 
and the spice-bearing lands of southern and eastern Asia; but this 
trade added little to knowledge of eastern geography, for the goods 
commonly changed hands many times at the trading cities along the 
caravan routes. In the fifteenth century, when the demand for 
eastern goods was stronger than ever before, the trade was reduced 
greatly (1) through the Turkish conquest of the regions crossed by 
the northern trade routes to the shores of the Mediterranean and the 
Black seas, and (2) through the heavy taxes levied by Egyptian rulers 
on goods coming through that country. These things encouraged 
the search for a sea route to the East, and resulted in the discovery 
of the route around Africa to India by Vasco da Gama (1498) and in 
the discovery of America by Columbus (1492). These discoveries 



24 ELEMENTS OF GEOGRAPHY 

changed the front of Europe from the Mediterranean to the Atlantic 
coast, and began a new period in history. The continued attempt 
of Spain to find a western route to the spice lands led to the first 
circumnavigation of the globe by Magellan (1519-1521), an achieve- 
ment which settled beyond doubt the question of the general form 
>f the earth. 

The coasts of North America and South America were explored 
during the sixteenth and seventeenth centuries, and most of the 
shore-line of Australia during the latter period. During these centu- 
ries, too, the commercial nations of western Europe founded colonies 
and trading posts in many parts of the world. With the growth of 
colonies and the improvement of navigation, commerce became world- 
wide, and the oceans came to be highways connecting the continents, 
rather than barriers separating them.' Much of interior North America 
was explored in the eighteenth century, while Africa and Australia 
were opened up during the nineteenth. 

During late years, knowledge of the earth's surface has been 
extended rapidly, the latest advances being the reaching of the 
North Pole by Commander Peary in 1909, and the South Pole by 
Captain Amundsen in December, 191 1. Much remains to be 
learned about the earth. The largest unexplored areas are those 
in polar regions, but there are little known areas in each of the 
continents except Europe. Only relatively small regions have been 
studied in detail by modern methods. 

Maps and Map Reading 

What is known of the earth's surface may be represented in vari- 
ous ways, — by globes, models, and maps. Globes have the great 
advantage of showing without distortion the distribution of land and 
sea, and Other large surface features. It is not practicable, however, 
to make them large enough to show minor features, and, even apart 
from this, they are not suited to all purposes. Models, or relief maps, 
reproduce on a small scale the unevenness of the earth's surface. In 
order that the elevations may stand out clearly, their height is exag- 
gerated greatly on most models, which are likely, therefore, to give 
false impressions. 

Map projections. The necessity of representing part or all of the 
earth on a flat surface led very early to the makjing of crude maps (Fig. 
12). It is, of course, impossible to show the rounded surface of the earth 



EARTH RELATIONS 



25 



on a flat surface without exaggerating or reducing certain parts, so that 
each of the many methods (projections) devised from time to time 
for representing the meridians and parallels of a globe on a plane 
surface, involves more or less distortion. 

Almost all sailing charts and many maps of the entire world 




Fig. 14. Map on Mercator's projection. 



are made on Mercator's projection 
(Fig. 14), named for the inventor. 
The principle involved in this pro- 
jection may be understood by imag- 
ining a cylinder to be placed over a 
globe, as shown in Fig. 15. Next 
let straight lines be drawn from the 
center of the globe through various 
points on its parallels and meridians, 
and projected until they touch the 
cylinder. When the cylinder is cut 
down one side and opened out flat, 
there is a network of parallels and 
meridians, the former horizontal 
lines, the latter vertical. Features 
of any kind may now be put in 




Fig. 15. Diagram to illustrate the 
principle of the Mercator projection. 



26 



ELEMENTS OF GEOGRAPHY 




according to their 
known latitude and 
longitude. A map 
on Mercator's pro- 
jection is accurate 
at the equator, but 
exaggerates areas 
more and more as 
the poles are ap- 
proached. Thus 
Greenland (Fig. 14) 
appears to be about 
half as large as 
North America on 
a Mercator's map, 
while in reality it 
is less than one- 
fifteenth as large. 

Figs. 16 and 17 
show a portion of 
Europe on the con- 
ical projection, and 
also the way in 
which such a map 
is made. Imagine 
straight lines 
drawn from the 
center of the globe 
(Fig. 16) through 
numerous points 
on its parallels and 
meridians, and ex- 
tended until they 
intersect the cone, 
which is so placed 
as to touch that 
parallel on the 

globe which runs 

Fig. 17. Portion of surface of cone spread out, t u rm]fr u f u e rPnTPr 

representing map. PP the parallel where the cone coin- Liirougn uie center 

cided with the sphere. of the district to be 



Fig. 16. Diagram to illustrate the principle of the 
conical projection. Cone ABC imposed upon sphere, 
touching it at PP. 




EARTH RELATIONS 



27 




Fig. ] 
hachures. 



.. Map representing relief by 
(U. S. Geol. Surv.) 



mapped. When the cone is cut open from the apex and flattened 
out (Fig. 17), the parallels are arcs of concentric circles, while the 
meridians are radiating straight lines. Some form of this projection 
is generally used for mapping 
individual countries. It in- 
volves comparatively little dis- 
tortion. In practice, maps on 
these and many other projec- 
tions are constructed by math- 
ematical means, without the use 
of a globe. ■ 

Representation of relief on 
maps. The surface of the land 
is uneven, and it is a matter of 
importance, in many cases, to 
show the unevennesses {relief) 
on maps. This is done in vari- 
ous ways. One method is by 
shading, — different colors or 
shades representing different elevations (see maps at end of book). 
Another. method is by hachures (Fig. 18) — lines drawn in the direc- 
tion in which the land slopes. Where slopes are steep, the lines are 
made short and heavy; where gentle, longer and lighter. Such maps 
give only a general idea of the form of the land. 

Much more exact information may be had from contour-line 
maps. In order to read contour-line maps, it is necessary to know 
that contours are lines drawn on maps to express relief, and that any 
given line runs through points of the same elevation above sea-level. 
This will be understood readily by reference to Figs. 19 and 20. 
Fig. 19 shows a model of an ideal landscape viewed from above, on 
which lines have been drawn connecting places of equal elevation. 
In Fig. 20 the above lines are shown alone; this is a contour map 
of the region represented by the model. By comparison of the model 
and map it will be seen that where the slopes of the former are steep, 
the lines of the latter are close together, and vice versa. The vertical 
distance between two adjacent contour lines is the contour interval. 
The contour interval varies on different maps. In regions of low 
relief an interval of 10 or 20 feet is used generally; in mountainous 
areas an interval of 500 or more feet has to be used in some cases in 
order to avoid having the lines too close together to be read. In 



28 



ELEMENTS OF GEOGRAPHY 



the map of Fig. 20, the interval is 20 feet, the exact value of the 100 
and 200 foot lines being indicated. By counting the lines it will 
be seen that the top of the hill to the left of the river is more than 



■ ■ \ . \ 


\ 


/ --'^£&B 


£9HP r ?"~ 




I \ \ 






^— agHjH 






' 


^-rs 


\ 


. 






' ■ 1 


\ V 


V —~ 


-riMwB^B 






\\\U 


~"~jNj 








"' ^^0 


Pf»i 


— ~— "'T&M 












" ~"~'Z%~Jr 


; 























Fig. 19. Model of ideal landscape. (U. S. Geol. Surv.) 




Fig. 20. Contour map of the area shown in Fig. 19. (U. S. Geol. Surv.) 

260 feet above the level of the ocean in the foreground. It cannot be 
280 feet high, however, for no 280 foot line is drawn. A comparison 
of the model and map will show also how valley depressions are shown 
by contours. 



EARTH RELATIONS 29 

Scale of maps. The relation between distance on a map and 
actual distance on the surface of the earth is shown by the scale. 
It is sometimes expressed by a fraction. Thus -sriro" means that 
one inch on the map represents 62,500 inches (almost a mile) on the 
earth's surface. As expressed on most maps, the scale explains itself. 
It is important to note the scale of every map studied, in order to 
understand the space relations involved. 



Terrestrial Magnetism 

The earth is a great magnet, and, like the small magnets with 
which we are familiar, has two poles. One of these poles is called 
the North Magnetic Pole and the other the South Magnetic Pole. 
One end of the compass needle points toward one of these poles, 
and the other toward the other. If we were to follow the directions 
pointed by the compass needle, w T e would be led to the North Mag- 
netic Pole in the one case, and to the South Magnetic Pole in the other. 

The magnetic poles are far from the geographic poles, the true 
north and south points, and they are not exactly opposite each 
other. Their positions appear to shift a little from year to year, but 
the change is not known to be great. The North Magnetic Pole is in 
latitude about 70 N., and in longitude 97 or 98 W., while the South 
Magnetic Pole is in latitude 72 25' S., and longitude 155 16' E. 

Since one end of the magnetic needle points to the North Mag- 
netic Pole, it follows that the compass does not indicate true north 
and south in many places. At points north of the North Magnetic 
Pole, the " north" end of the needle points in a southerly direction. 
At points east of the same pole, it points westward, and at points 
west, eastward. The departure of the needle from the true north 
and south is magnetic declination. A line connecting places of no 
declination is an agonic line, and lines connecting places of equal 
declination are isogonic lines. 

Fig. 21 shows an agonic line in the United States running from 
Lake Superior to South Carolina. Along this line the compass needle 
points due north and south. At all places east of this line the needle 
points west of true north, and such places have west declination. All 
places west of the agonic line have east declination. In general, 
declination increases with increasing distance from the agonic line., 
At New York City the declination is about io° W., and in Maine it 
is more than 20 W. at a maximum. At Chicago the declination is 



3° 



ELEMENTS OF GEOGRAPHY 



about 3 E., at Denver about 13 E., at San Francisco about 16 E., 
and in the state of Washington more than 20 E. 

It will be seen that it is necessary to know the magnetic declina- 
tion of a region, if the compass is to be used there for determining 
directions accurately. The declination being known, the compass is 
of great value to travelers through forests and other tracts which 
have no roads or trails. The compass, too, is in constant use on the 
sea, where vessels are guided by it. 




Fig. 21. Lines of equal magnetic declination for the United States, 1902. 
The heavy line is an agonic line, or line of no declination. (U. S. C. and G. Surv.) 

The declination at a given place does not remain quite constant. 
The declination at Chicago, for example, has shifted more than 2 ° 
since 1820. With increased travel over the oceans, there is great 
need of accurate knowledge of compass declination and its variations. 
Hence vessels have been specially built and equipped to permit the 
greatest possible accuracy in making magnetic observations covering 
all the oceans of the world. 



Questions 

1. The horizon of a given observer increases as he rises. What does this prove 
concerning the shape of the earth's surface at that place? What additional infer- 
ence could be made from the fact that as he ascends his horizon remains circular? 



EARTH RELATIONS 



3i 



2. At places east of a given point the sun rises and sets before it does at that 
point. At places toward the west it rises and sets after it does at the station in 
question. What does this indicate as to the surface of the earth? 

3. Why do the sun's rays never fall vertically in latitudes higher than 23^°? 

4. Certain crops are said to mature faster in western Canada than farther 
south in the United States. Suggest a logical reason for this. 

5. How would the seasons at Chicago (42 N.) be changed if the axis of the 
earth were inclined 45 , rotation remaining as now? 

6. An ancient philosopher concluded, from observing the changes in the 
altitude of stars as he traveled, that the earth is not a very large sphere. What 
fact could have led him to this conclusion? 

7. Two cities about 690 miles apart, on the same meridian, are located in 
latitude 42 N. and 32 N., respectively. From these facts determine approximately 
the circumference of the earth. 




Fig. 22. Diagram showing the apparent daily course of the sun to an observer 
in northern United States, at different seasons. 



8. Fig. 22 shows the apparent daily course of the sun to an observer in northern 
United States at different seasons. (1) Which of the paths indicated is followed 



by the sun in mid-winter? Spring? 
reasons may be inferred from the 
diagram for the greater heat of 
summer? (3) Draw a similar dia- 
gram for 45 south. 

9. Fig. 23 shows the apparent 
course of the sun to a given observer 
on a certain day. (1) In about 
what latitude is the observer? (2) 
What is the time of year? (3) What 
are the conditions of light and dark- 
ness at the same time in the corre- 
sponding latitude of the opposite 
hemisphere? 



Mid-summer? Autumn? (2) What two 




Fig. 23. Diagram showing the appar- 
ent course of the sun to an observer at A 
on a certain day. 



32 ELEMENTS OF GEOGRAPHY 

10. What is the difference in longitude of two places having a difference in 
time of six and one-half hours? 

ii. What is the difference in solar time between New York City (74° W.) 
and Chicago (87 36' W.)? 

12. The altitude of the sun at a given place at noon at the time of equinox 
is 50 . What is the latitude of the place? 

13. In what latitudes is the altitude of the sun 20° at noon at the time of 
equinox? 

14. In what latitudes has the sun a noon altitude of 30 at the time of the 
summer solstice? 

15. What is the altitude of the sun at the equator at noon at the time of the 
summer solstice? 

16. If you wished to go due north from San Francisco, how would you be 
guided by a compass? 

References 

Chamberlin and Salisbury: College Geology, Chs. XII, XIII. (New York, 

1909.) 

Chamberlin and Salisbury: Earth History, Vol. II, Chs. I, II. (New 

York, 1906.) 

Comstock: A Textbook of Astronomy. (New York, 1903.) 

Johnson: Mathematical Geography. (New York, 1907.) 

Mill: The International Geography, pp. 7-13. (New York, 1905.) 

Moulton: An Introduction to Astronomy. (New York, 1906.) 

Poor: The Solar System. (New York, 1908.) 

Todd: A New Astronomy. (New York, 1897.) 

Young: A Textbook of General Astronomy. (Boston, 1893.) 



CHAPTER III 
RELIEF FEATURES OF THE EARTH 

The surface of the land is uneven. The lowest lands are below 
sea-level, and the highest point (Mt. Everest, in the Himalaya Moun- 
tains) is more than five and one-half miles above sea-level. The 
relief of the land surface is therefore not far from six miles. Com- 
pared with the diameter of the earth, even the loftiest mountains are 
slight elevations, for the height of Mt. Everest above the sea is equal 
to only ttVf part of the polar diameter of the earth. On a globe 
10 feet in diameter this would correspond to one-twelfth of an inch. 

The sea bottom also is uneven, and its relief is a little greater than 
that of the land. Since the highest points of land are nearly six miles 
above the sea, and the lowest parts of the sea bottom about six miles 
below, the relief of the surface of the solid part of the earth {litho sphere) 
is almost twelve miles. If its surface were even, the water of the ocean 
would cover the whole earth to the depth of about 9,000 feet. 

Relief Features of the First Order 

Continents and ocean basins. The average elevation of the 
lands above sea-leyel is a little less than half a mile, while the average 
depth of the oceans is about two and one-half miles. The continents 
are therefore, on the average, nearly three miles above the bottoms 
of the ocean basins. It is fortunate that the general elevation of the 
land above sea-level is not greater than it is in middle and high lati- 
tudes. Were it equal to the average depth of the oceans, most of 
each continent would be too high and cold to support a dense popula- 
tion. The continents and the ocean basins are relief features of the first 
order. 

The oceans have an area (143,000,000 square miles) nearly three 
times as great as that of the lands (54,000,000 square miles). The 
shallow water about the borders of the continents rests on surfaces 
(the continental shelves; Fig. 24) which are, in reality, parts of the con- 
tinents. The continental shelves are but little below the lowlands of 

33 



34 ELEMENTS OF GEOGRAPHY 

many coasts, and they are far above the ocean bottoms. Since the 
seas not only fill the ocean basins, but spread over the continental 
shelves as well, their area is greater (by some 10,000,000 square miles) 
than that of the true ocean basins. The latter are a little more than 
twice as extensive as the continental plateaus. At the sea-ward edges 

Mountains 

Plateau ^-^ /X _^ ™,w„.. 



Fig. 24. Diagram to show the distinction between an elevated continental 
area and an ocean basin. The steep slope (much exaggerated) at the left of the 
ocean basin is the line of contact between the two, and is the real border of the 
continental area. The ocean covers the lower part of the continental tract, 
namely, the continental shelf. The diagram also shows the general relation 
between low mountains, such as the Appalachians, a low plateau, and a coastal 
plain. The continental shelf, is a continuation of the coastal plain. 

of the continental shelves there are rather steep slopes down to the 
ocean basins. Portions of the continental shelves may have been 
formed by the long-continued off-shore accumulation of sediments 
from the land ; other parts are due to the submergence of former land 
areas; and still others are platforms resulting from the wearing back 
of the land by waves. 

Many islands stand on the continental shelves, and represent 
higher areas whose lower surroundings are drowned. In many cases 
a slight elevation of the continental shelf, or a slight lowering of the 
sea, would join these islands to the mainland. Thus a change of only 
300 feet would transform most of the area of the Baltic and North 
seas into land, and unite Great Britain with the continent. While 
such a change would add much new land to Europe, it would affect 
adversely the climate and commerce of large areas of existing land 
(How ?). It would also modify greatly conditions in Great Britain. 
Isolation from the continent has freed the United Kingdom from the 
need of maintaining a large standing army, and so added many thou- 
sands of men to the productive population. On the other hand, it 
compelled the development of extensive sea interests, and the main- 
tenance of a large navy to protect them. Most oceanic islands not 
on the continental shelves are volcanic cones, or coral islands 
associated with them. Their combined area is only about three- 
fourths that of the state of Illinois. 



RELIEF FEATURES OF THE EARTH 35 

Grouping of the continents. The northern hemisphere con- 
tains more than twice as much land as the southern. If the earth be 
divided into two hemispheres, one with its center in England and 
the other in New Zealand (Fig. 25), the first would contain about 
six-sevenths of all the land, and might be called the land hemisphere, 



Fig. 25. Land and water hemispheres. 

while the other would contain only about one-seventh of the land, 
and might be called the water hemisphere. Even in the land hemi- 
sphere, however, the water would cover rather more than half the 
surface, while in the water hemisphere it would cover about fourteen- 
fifteenths of it. Since the northern hemisphere contains two-thirds 
of the land, and a still larger proportion of the productive land, it 
has always supported a vast majority of the human race. 

The irregular grouping of the continents follows no known law. 

Origin of relief features of the first order. The ocean basins 
and the continental platforms seem to have been very much as they 
now are for millions of years. It is probable that the ocean basins 
have sunk below the continents, rather than that the continents have 
been raised above the ocean basins. The reason for this belief is that 
the earth is cooling, and therefore shrinking, and shrinking means 
that the outside is on the average getting nearer to the center. This 
must result in a sinking of the surface, in some places at least. 

Past changes. If the sea bottom were to sink now, the ocean 
basins would hold more, and some of the sea-water would be drawn 
off the continental shelves. If the bottoms of the ocean basins were 
to sink 600 feet, or a little more, all the water would be drawn off the 



36 ELEMENTS OF GEOGRAPHY 

continental shelves, and they would then become land. If the con- 
tinents were to sink, the sea would spread over their low borders, 
reducing the area of land. The history of the earth teaches that the 
areas of ocean and land have changed somewhat from time to 
time. The lower parts of the continents have been drowned repeat- 
edly, but it is not known that any part of the deep sea bottom was ever 
land, or that any part of the land was ever beneath a deep sea. 

Relief Features of the Second Order 

The more strongly marked features of the continents and of the 
ocean basins are relief features of the second order. The continental 
areas are made up of plains, plateaus, and mountains. Some of their 
relations are shown in Fig. 24. 

Plains. Plains are the lowlands of the earth, yet they cannot be 
defined in terms of height above the sea. They may be but a few 
feet above it, or they may be hundreds or even thousands of feet 
above; but if so high as a thousand feet, they are generally far from 
the sea, and distinctly lower than some of the other lands about them. 
Plains differ widely among themselves, not only in height, but in 
position, size, shape of surface, fertility, origin, and in various other 
ways. Different names are given to various sorts of plains, the 
names being intended to call attention to some one feature. Impor- 
tant classes of large plains are coastal plains, which border the sea, 
and interior plains, which are far from the sea, or separated from it by 
high lands. The Atlantic and Gulf coastal plains illustrate the first 
class, while a large part of the area between the Appalachian Moun- 
tains and the Rocky Mountains is a great interior plain (Fig. 148). 



Mountains 




Fig. 26. Diagram to illustrate the relations of mountain, plateau, plain, 
ocean basin, and ocean deep. 

Plateaus. Plateaus are highlands with considerable summit areas; 
but no great elevation is necessary to make a flattish area of land a 
plateau. In general, a plateau is so situated as to appear high from 
at least one side. Thus if a coastal plain rises gradually from the sea 



RELIEF FEATURES OF THE EARTH 37 

to a height of 200 feet, and then rises by a steeper slope to another 
broad tract of land which stands 200 feet higher (Fig. 26), the upper 
tract would be called a plateau, not so much because of its altitude 
above sea-level, as because of its distinct rise above the plain along 
one side of it. The Piedmont Plateau, which lies between the Appa- 
lachian Mountains and the Atlantic Coastal Plain is not very high, 
but it is enough higher than the Coastal Plain to be distinctly set off 
from it. A large part of this plateau is, however, not so high as 
much of the great interior plain of the continent. 

Some plateaus lie between mountains on the one hand and plains 
on the other, as in the case of the Piedmont Plateau. Others lie be- 
tween mountains, as the plateaus of central Asia (Fig. 27), Mexico, 

Caucasus Mts, Himalaya Mts. Nan-Shan Mts. 



Fig. 27. Section across Asia, showing plateau between the Himalayas and the 
Nan-Shan Mountains. 




Fig. 28. Section across North America, showing plateaus between the 
mountains in the western part. 

and western United States (Fig. 28). Such plateaus do not appear 
higher than their surroundings. Other plateaus rise directly from 
the sea, as Greenland and parts of Africa. The total area of plateaus 
is great, though less than that of plains. 

Mountains. Mountains are conspicuously high lands which have 
slight summit areas (Fig. 29). The tops of the loftiest mountains are 
between five and six miles above the sea, but most mountains have 
.not half this height.* The highest mountains tower above any 
plateaus, but many mountains are lower than the highest plateaus. 
Few mountains reach the height of the Plateau of Tibet, 15,000 to 
16,000 feet. 

Mountains are unlike plateaus of similar elevation in having little 
area at the top. In the case of mountain peaks, this is shown by 
the name. A mountain ridge or range may be long, but in most cases 
its crest is narrow (Fig. 243). Numerous peaks or ranges may be 
associated, making a mountain group or mountain chain; but even 



38 



ELEMENTS OF GEOGRAPHY 



in great mountain groups there is no great unbroken expanse of 
high land. 

Where mountains rise abruptly to great heights above their sur- 
roundings, they are the most impressive and awe-inspiring features 
of the earth. In not a few cases they rise from low, warm plains 




Fig. 29. Mountains rising conspicuously above a plain. Southern California. 



to such heights that their summits always are covered with snow 
(Fig. 30). Nowhere else are such extremes of climate found so 
close together. 

Mountains are the third of the three topographic types of the 
second order, as they appear on the lands of the earth. In this group- 
ing of mountains, only great groups or systems of mountains, such as 
the Appalachians, the Rockies, the Alps, the Himalayas, and the 
Andes, are considered. Since the term "mountain" is applied to any 
point or ridge of such steep slopes and so much above its surroundings 
as to be conspicuous, it follows that many elevations called mountains 
(Fig. 30) do not belong to the great physiographic type which is to be 
brought into contrast with plains and plateaus. 

It is noteworthy that mountain ranges are situated in general 
near the edges, rather than in the interiors, of the land masses, and 
that most of the loftier mountain chains are not far from the shores 
of the greatest ocean. The continental slopes to the Pacific Ocean 
are therefore shorter and steeper than those to the Atlantic and 
Arctic oceans. It is estimated that slightly more than half the land 
of the world drains to the latter oceans (Atlantic, 34.3%; Arctic, 



RELIEF FEATURES OF THE EARTH 



39 




Fig. 30. Sketch showing range from tropical vegetation on lowlands, to snow- 
fields on mountain, a common condition in the tropics. Orizaba, Mexico. 
(From photograph by Land.) 




Fig. 31. Map showing drainage areas tributary to the different oceans, and 
areas of interior drainage (shaded). 



40 ELEMENTS OF GEOGRAPHY 

I 6-S%). One-seventh (14.4%) drains to the Pacific, and about one- 
eighth (12.8%) to the Indian Ocean. The drainage of the rest of the 
land (22%) fails to reach the sea, and is lost in dry interior basins. 
Some of these basins, as in central Asia and western United States, 
are nearly surrounded by high mountains. Fig. 31 shows the areas 
tributary to the several oceans. 



Subordinate Topographic Features 

The surfaces of most plains and plateaus are uneven, while the 
very name of mountain suggests ruggedness. Irregularities of surface 
consist of elevations, such as ridges and hills, above the general level, 
and of depressions, such as valleys and basins (depressions without 
outlets) below it. The elevations and the depressions are bordered 
by slopes, which, when steep, are called cliffs. Ridges, hills, valleys, 
basins, flats, and cliffs affect mountains, plateaus, and plains; but in 
most cases they are more pronounced in mountains and plateaus than 
on plains. These minor unevennesses of surface are topographic 
features of the third order. The key to their history is found in changes 
now taking place on the land (Chapter XV), or in those which have 
taken place in recent times. 



Comparison of the Continents 

The position, form, size, and general relief of the continents are 
of fundamental importance, since these things determine, in large 
measure, their fitness for human occupation. Europe, the smallest 
continent except Australia, lies almost entirely in the north temperate 
zone. It widens rapidly toward the south, so that its east and west 
extent along the line of the Mediterranean, Black, and Caspian seas 
is nearly three times that along the Arctic Ocean. No 'other conti- 
nent has an outline so irregular. Great arms of the sea extend far 
inland, modifying climate and helping commerce by bringing most 
parts of the continent into close contact with the sea. More than 
half of Europe is less than 600 feet above sea-level, and only one-sixth 
is over 1,500 feet. Many rivers serve as natural highways into the 
interior. Some of those in the west are unfrozen throughout the year. 
Europe has no tropical section, and no dry desert. 

Asia, the largest of the continents, is nearly 4^ times the size 
of -Europe, and nearly 5^ times as large as the United States. It 



RELIEF FEATURES OF THE EARTH 41 

extends somewhat farther north than Europe, and much nearer the 
equator. Less than one-fourth of Asia is below 600 feet above the 
sea, and about one-sixth is above 6,000 feet. The average elevation 
is nearly three times that of Europe. A central region of high pla- 
teaus and mountains receives little rain, and is of slight value to man. 
The longest drainage slopes are toward the Arctic. Because of these 
things, one-half of Asia is relatively inaccessible. Asia has only 
about one-third as long a coast-line as Europe in proportion to its 
area. Its great size and relatively compact form make it the conti- 
nent of, climatic extremes. From a physical standpoint Europe and 
Asia form one continent (called Eurasia), but for historical and other 
reasons they usually are separated. 

Australia is only a little larger than the United States, and is 
divided approximately in halves by the Tropic of Capricorn. The 
coast, though less regular than that of Africa and South America, has 
few harbors compared to Europe and North America. Because of 
its position, size, compactness, and topography, much of interior 
Australia is arid (p. 167). Australia is the most isolated of the 
continents. 

About two-thirds of Africa are within the tropics. Broadly 
speaking, the continent consists of a great plateau, bordered in places 
by a very narrow coastal plain. At the south, the plateau is 3,000 to 
5,000 feet above sea-level; at the north, 1,000 to 2,000 feet. Only 
one-eighth of the land (less than in any other continent) is below an 
elevation of 600 feet. The rivers descend in rapids or falls to the 
coastal lowlands. More than one-third of the continent is desert, 
while large areas in addition are semi-arid. Africa has the most 
regular coast of any continent. Europe, the most highly indented, 
has more than six times as much shore-line as Africa, in proportion 
to its area. Although one of the most ancient civilizations had its 
seat in Egypt, Africa has remained to our own day the "dark conti- 
nent." The conditions indicated above have helped greatly to 
bring this about. The fact that much of the coast was devoid of 
harbors, and that navigation of even the larger rivers was interrupted 
near their mouths by falls and rapids, delayed exploration, conquest, 
and commerce. Both the vast deserts and the dense equatorial forests 
retarded native progress, and discouraged European settlement. 

Like Africa, South America is largely within the tropics and is 
very compact, with few great indentations, peninsulas, or islands. 
On the other hand, the proportion of desert is much less, and of Iqw- 



42 



ELEMENTS OF GEOGRAPHY 



lands much greater. Two-fifths of South America are below 600 feet, 
and two-thirds under 1,500 feet. 

In North America, as in Europe, most of the land is in middle 
latitudes. Unlike Europe, North America presents its greatest width 
to the cold polar seas. North America ranks next to Europe and 
South America in the relative extent of its lowlands. Nearly one- 
third of the continent is below 600 feet, and nearly two-thirds below 
1,500 feet. The vast interior plain stretching from the Arctic Ocean 
to the Gulf of Mexico has an unequaled system of navigable water- 
ways. Except Europe, North America has the longest shore-line in 
proportion to its size. The greatest indentation, the Gulf of Mexico, 
affects the climate of eastern United States profoundly (p. 132). 
Except in the far north, most of the indentations have commercial 
importance. 

Questions 

1. South America and Africa have few islands about their borders. What 
does this suggest concerning the width of their continental shelves? Does it 
prove anything about the width? 




Fig. 32. Map showing valley-like depression extending across the continental 
shelf from the Hudson River. 



RELIEF FEATURES OF THE EARTH 43 

2. Soundings along the eastern coast of the United States have shown that 
depressions like river valleys extend across the continental shelf from the mouths 
of various rivers (Fig. 32). What was the origin of those parts of the continental 
shelf in which these depressions occur? 

3. From the comparison of the continents given on pages 40-42, which 
ones appear best fitted to contain the most advanced nations? Which ones seem 
least fitted to do so? 

4. Most people live on plains. Would it therefore be better, from the human 
standpoint, if the earth were without mountains? Reasons? 



CHAPTER IV 
THE NATURE AND FUNCTIONS OF THE ATMOSPHERE 

General Conceptions 

Relation to rest of earth. The atmosphere is often called an 
envelope of the earth. It is, however, a part of the earth, held by 
gravity to the rest of the earth, with which it moves through space. 
Air is essential to the life of the earth, and to most of the processes in 
operation on the earth's surface. It helps to distribute moisture, it 
makes the extremes of heat and cold less than they would be if it did 
not exist, and it is a leading factor in the formation of soil. Further- 
more, the atmosphere is not merely an envelope of the rest of the earth, 
for it goes down into the soil and rocks as far as there are holes and 
cracks, and its constituents are dissolved in the waters of sea and land. 

Weight of air. When the atmosphere is still, we are hardly 
conscious of its existence, but many familiar phenomena show that 
air is very substantial. Thus wind, which is only air in motion, may 
be so strong that trees and buildings are blown down by it. A wind 
blowing 30 miles an hour exerts a force of nearly 60,000 pounds on 
the side of a house 60 feet long and 20 feet to the eaves. The weight 
of the air may be shown in another way. If the air is pumped out 
of a cylinder whose top is covered by a thin piece of rubber, the rubber 
cover is pressed down into the cylinder. The force which presses it 
down is the weight of the air above. This shows that air is something 
real, has weight, and exerts pressure. The amount of its pressure, 
that is, its weight, is nearly 15 (14.7) pounds on every square inch of 
surface at sea-level. In other words, the weight of the air is equal to 
that of a layer of water completely covering the earth to a depth 
of 33 feet. The pressure of the air on the body of a man amounts to 
several tons, but this is not felt because it is balanced by the outward 
pressure inside the body. 

Density. The atmosphere is made up of gases. The particles 
of which the air is composed are nearer together at low altitudes than 
at high altitudes. At the bottom of the atmosphere the air is pressed 

44 



NATURE AND FUNCTIONS OF THE ATMOSPHERE 45 



Highest Mountam_ (6tnil es ) 
HighesJ;_Mountam_Asce„t (4'/ 2 ~mU e ^~^ 

Low CUmdsCk mile ) 



down by all the air above; at the height of 1,000 feet the air is 
pressed down by all above that level, and so on. Hence the lowest 
air is under most pressure and is densest. One-half the atmosphere 
(by weight) lies below a plane about 3.6 miles above sea-level, and 
three-fourths of it below a plane 6.8 miles above the same level. The 
highest mountain is almost six miles high, so that nearly three-fourths 
of the atmosphere lies below the level of its top. 

It is largely because the air is less dense at high levels that moun- 
tain-climbing is difficult. The body is not used to the lessened 
pressure, and it causes discomfort. The chief difficulty, however, 
comes from the fact that, though the climber may take in the same 
number of cubic inches of air 
each time he inhales, each cubic 
inch contains less oxygen, the 
higher he goes. 

Height. The decreasing 
density of air at high altitudes 
suggests that, at some distance 
above the land, the top of the 
atmosphere may be reached. 
Though its actual height is not 
known, something is known 
about it (Fig. 33). 

(1) The greatest altitude reached by any mountain-climber is 
about 24,000 feet. At this height there is air enough to make breath- 
ing possible to a climber. This shows that the air extends to a height 
of more than four and one-half miles. 

(2) Men have gone up in balloons to heights of nearly six miles. 
In some cases, the men in the balloons became unconscious at an 
elevation of about 29,000 feet, and in other cases, where oxygen was 
carried for breathing, the chief discomfort was from' cold. Balloons 
without men have risen ten miles. At this height the air is still 
dense enough so that the balloon did not sink. This shows that the 
air extends up more than ten miles. 

(3) On almost any clear night "shooting stars" may be seen. 
Shooting stars, or meteors, are small, solid bodies which come into the 
earth's atmosphere from space outside. They are very cold when 
they enter the atmosphere, for the temperature of space is very low 
(believed to be about — 459° F.). In passing through the atmosphere, 
meteors are heated by friction with the air, and when they get red-hot, 



Fig. 33. Diagram to show relative 
altitudes in the atmosphere. 



46 ELEMENTS OF GEOGRAPHY 

they glow and may be seen. The height at which they begin to glow 
has been calculated in some cases, and found to be, at a maximum, 
nearly 200 miles above sea-level. This shows" that the atmosphere 
is much more than 200 miles high, for the meteors must have come through 
the rare, cold, upper ~avr a long distance before becoming red-hot by fric- 
tion with it. 

From these considerations it appears to be certain that the air 
extends more than 200 miles above the rest of the earth, but how 
much more is unknown. Except for a few miles near its bottom, it 
is, of course, very thin (rare). 

Composition 

Principal constituents. The composition of the atmosphere is 
nearly the same at all times and at all places where it has been ana- 
lyzed. In its lower parts, at least, it is made up chiefly of two gases 
— (1) nitrogen, which makes up nearly 78 per cent of dry air, and (2) 
oxygen, which makes nearly 21 per cent. Some scientists think its 
composition at great heights may be very different from that below. 

Beside these two gases, there are several lesser constituents, two 
of which, carbon dioxide and water vapor, are very important. The 
former makes up about tooto by weight of the whole atmosphere, 
and its amount is nearly constant from day to day, and from year to 
year. Water vapor is water in particles too small to be seen. The 
total amount in the atmosphere is not known to vary much, but the 
amount varies greStly from place to place, and it varies much from 
time to time in the same place. Even in the driest deserts the air is 
never without water vapor. Several other gases exist in the air, but 
among them ozone only is known to be of much importance. 

The gases of the air are mixed with one another, and each of them 
retains its own qualities in the mixture. The oxygen behaves much 
as if no nitrogen were present, and the nitrogen as if there were no 
oxygen. 

Impurities. The air always contains some gases which must be 
looked upon as impurities, though they are not necessarily harmful, 
to life. Some such gases arise from the burning and decay of organic 
matter, others from chemical processes used in manufacturing, and 
still others from volcanic and other vents in the earth's crust. 
Although the total amount of gas which enters the air in these ways 
is small in comparison with the volume of the atmosphere, it would 



NATURE AND FUNCTIONS OF THE ATMOSPHERE 47 

doubtless be most impressive could it be stated in terms of weight or 
volume. For example, it is estimated that at least 1,000,000,000 
cubic feet of natural gas escape unused into the air each day in the 
United States. Quantities of gas are poured into the air, too, from 
chimneys. In great manufacturing centers, gases from chimneys may 
be a source of discomfort to the people. The air always contains, 
as impurities, numerous solid particles, principally germs or other 
organic matter, and the commoner forms of dust. These vary in 
amount and character from place to place, and from time to time. 



Relations of the Different Constituents to Life 

Nitrogen. The various constituents of the atmosphere serve 
different purposes. Nitrogen is inactive. Though it enters the 
lungs with oxygen in breathing, it does not appear to be of direct use 
to animals. Indeed, its chief function in relation to life is often said 
to be "to dilute the oxygen." It is important to note, however, that 
indirectly nitrogen is of great importance to both plant and animal 
life. Man requires for his food considerable quantities of proteids, 
substances which contain nitrogen combined with other things. He 
obtains the proteids either from plants, or from animals which derived 
them from plants. Most plants use the small quantities of nitrogen 
compounds in the soil in forming proteids. Nearly all crops, if grown 
year after year in the same place, take out so much of the nitrogenous 
matter as to decrease the fertility of the soil. A few plants, such as 
clover, alfalfa, peas, and beans, add nitrogen to the soil. Certain 
bacteria associated with these plants take nitrogen from the air and 
combine it with other elements, and the plants then store the com- 
bined nitrogen in their roots, stalks, etc. It is therefore highly advan- 
tageous to grow nitrogen-fixing plants in rotation with other crops, 
and turn them under the soil. The nitrogen of the air is also drawn 
upon directly for the manufacture of fertilizers by electric processes. 
The pressure of the air, the force of the wind, and all other mechanical 
effects of the atmosphere are due largely to the nitrogen, for it makes 
more than three-fourths of the air by weight. 

Oxygen. Oxygen from the air is consumed all the time by animals. 
Air-breathing animals take it from the air directly, and water-breath- 
ing animals take it from the water in which it is dissolved. The 
energy expended in human activities is derived from a union of the 
carbon of the blood with the oxygen taken into the lungs. The 



48 ELEMENTS OF GEOGRAPHY 

product of the combination {carbon dioxide) is breathed back into the 
air. Oxygen is consumed by plants also, especially by green plants, 
and it is used wherever combustion (burning) or decay is going on, 
for combustion is primarily the union of oxygen with carbon, and 
decay is very slow combustion. The heat developed by combustion 
(as of coal) warms houses, and produces steam to run trains, drive 
machinery, and serve man in numerous other ways. Oxygen from 
the air combines with various constituents of rocks to form new com- 
pounds, and in so doing helps to form soil (p. 261). 

In spite of the fact that oxygen is being consumed all the time, 
its amount does not appear to grow less, from year to year. We infer, 
therefore, that it is supplied to the air about as fast as it is used up. 
Plants break up the carbon dioxide of the air into carbon and oxygen, 
and set some of the oxygen free. This is the greatest source of supply. 
Small amounts of oxygen also reach the atmosphere from volcanic 
vents, and in other ways. It will be seen that plants, through their 
relation to oxygen and nitrogen, play an important part in supplying 
animals with both these elements. 

Carbon dioxide. The carbon dioxide (C0 2 ) of the atmosphere, 
though a small constituent, is extremely important. It is being 
produced constantly by the burning of all kinds of fuel and 
by the decay of all organic matter. It is also added to the air by 
animal respiration. Every 1,000,000 human beings exhale about 2.5 
tons per hour. It also issues from many volcanic vents in great 
quantities. 

From these various sources, carbon dioxide is supplied to the 
atmosphere rapidly. About 75 per cent of common bituminous coal 
is carbon. The carbon of a ton of such coal, united with oxygen 
from the air (3 ibs of carbon unite with 8 lbs of oxygen), would make 
more than 2^ tons of carbon dioxide, all of which goes into the 
atmosphere. A ton of hard coal, which contains more carbon, would 
produce still more carbon dioxide. The railroads of the United 
States alone burn about 100,000,000 tons of coal yearly. This means 
about 275,000,000 tons of carbon dioxide from that one source. 
Nearly a billion tons of coal are mined each year, and most of this is 
burned. When all sources of carbon dioxide are considered, it seems 
safe to say that carbon dioxide is being supplied to the atmosphere 
at the rate of about 75 tons per second. 

Because of its close relations to combustion, respiration, and 
decay, the amount of carbon dioxide in the air of cities is greater than 



NATURE AND FUNCTIONS OF THE ATMOSPHERE 49 

in the open country. The amount in the air of London occasionally 
becomes five times the normal quantity, while in badly ventilated 
school-rooms, theaters, and workshops, it is sometimes ten times the 
normal amount. The conditions which lead to larger amounts of 
carbon dioxide in city air usually mean a corresponding increase in 
the amounts of various other harmful gases. Such conditions are 
injurious to health, and tend to make the residents of a large city 
less robust than the inhabitants of the country. The widespread 
movement to "purify city air," largely by the elimination of smoke, 
is an attempt to remedy these conditions. 

In spite of constant additions, the amount of carbon dioxide in 
the air does not increase permanently enough to be noted. This gas, 
therefore, must* be taken out of the atmosphere about as rapidly as 
it comes in. It is taken from the air chiefly (1) by green plants, of 
which it is the main food, and (2) by uniting with mineral matter 
in the solid part of the earth. It supports not only most plants, but 
indirectly most animals, for the latter feed on vegetation, or 
on other animals that live on plants. By uniting with mineral 
matter it helps to form soil. 

It will be seen that some of the CO2 is making a continuous round 
of change. It is taken out of the air by plants, and its constituents, 
notably carbon, become a part of the plant. In this process some of 
the oxygen is set free in the air. The carbon of the plant is then 
burned, either in a fire or by decay, and the carbon dioxide thus 
produced passes back into the air, to be used by plants again. Much 
carbon dioxide goes through this round each year, for much vegeta- 
tion grown during one growing season is burned or partially decays 
before the next. 

The supply and loss of carbon dioxide so nearly balance that no 
change in the amount of this gas in the air is noted from year to year ; 
but it seems quite possible that, in the course of long periods of time, 
the supply may have exceeded the loss, or that the loss may have 
exceeded the supply. 

Small as the amount of carbon dioxide is, it has still other impor- 
tant functions. The earth is constantly radiating heat into space, 
somewhat as a hot stove radiates heat into its surroundings, and car- 
bon dioxide has the power of holding much of this heat. It therefore 
serves as a blanket to hold in the heat of the earth, and, thin as the 
blanket is, it is more effective, in this respect, than the denser blanket 
of oxygen and nitrogen. If it were thicker, it would be still warmer. 



5 o ELEMENTS OF GEOGRAPHY 

If the amount of this gas were doubled, it is thought that the tem- 
perature of high latitudes would be notably increased, possibly enough 
to melt the ice of Greenland. 

A considerable decrease in the amount of carbon dioxide in the air 
may have been chiefly responsible for several widely separated periods 
of much lower temperature in the distant past, when great areas in 
various parts of the world were covered with snow and ice. Some of 
these areas are within the tropics, and now have very warm climates. 

Water vapor. The water vapor in the atmosphere is a variable 
quantity. It is all the time entering the atmosphere by evaporation, 
and it is all the time being condensed and precipitated from the 
atmosphere as rain, snow, etc., to be again evaporated, condensed, 
and precipitated. The larger part of both water vapor and carbon 
dioxide is in the lower part of the atmosphere. Like much of the 
carbon dioxide, the water vapor is making continuous rounds. Its 
precipitation supplies the water for wells, the flow of springs, the main- 
tenance of lakes, streams, and glaciers, and for the life of plants and 
animals. The bodies of animals, including human beings, are about 
four-fifths water. The tissues of annual plants are three-fourths 
water; of perennials, nearly half. To produce a bushel of corn, from 
10 to 20 tons of water are required. 

The amount of water vapor which the atmosphere is capable of 
containing at any time depends on temperature; but other things, 
such as the available supply, help to determine the amount which 
there is in the air in any one place. Like the carbon dioxide, the 
water vapor of the air helps to keep the earth warm. 

Ozone. Ozone is the only other important constituent of the 
atmosphere. Its amount is greater over the ocean than over the land, 
greater in the country than in the city, greater in winter than in 
summer, and in summer, usually greater after thunder-storms. 
Ozone, which is an unstable form of oxygen, has powerful bleaching 
and disinfecting properties. Interesting claims are also made con- 
cerning its health-giving properties. Its real value in this respect 
is, however, not known, and in more than minute quantities it is 
injurious to man. It is probable that its chief value to health lies 
in the fact that its presence is a guaranty of air free from the 
injurious products of organic decay. Its value as a disinfectant has 
led to its manufacture for that purpose. 

Dust. All the solid particles held in the air are dust. They are 
not ordinarily seen except on dry, windy days, but dust from the air 



NATURE AND FUNCTIONS OF THE ATMOSPHERE 51 

is constantly settling everywhere, indoors and out, whenever the 
air is dry. Dust may be seen readily indoors if a room is darkened 
and light allowed to enter through a narrow crack or small hole. 
Even air which appears clear may in this way be seen to contain 
countless particles of solid matter. The amount of dust is sometimes 
very great, as over cities, and in dry and windy regions. During the 
fogs of February, 1891, it was estimated that the amount of dust 
deposited on roofs in and near London was six tons per square mile. 
One effect of breathing dust-polluted air is a greater prevalence of 
diseases of the lungs, like tuberculosis. 

Some years ago a method was devised for counting the dust 
particles in a given volume of air. The result showed that in the 
air of great cities there are hundreds of thousands of dust particles 
in each cubic centimeter (a cubic centimeter is less than z /i6 of a cubic 
inch) of air; and that even in the pure air of the country, far from towns 
and factories, there are hundreds of motes per cubic centimeter. It 
has also been estimated that " every puff of smoke from a cigarette 
contains about 4,000 million separate granules of dust." The 
amount of dust in the air is greater over the land than over the sea, 
and in the lower atmosphere than in the upper. Like carbon diox- 
ide and water vapor, most of the dust is found below an altitude 
of 10,000 feet. Its relative absence at high altitudes increases the 
intensity of the sunshine there by day, and helps to bring about 
low temperatures at night. 

Dust consists of (1) inorganic materials, such as tiny particles 
of mineral matter blown up from dry roads and fields or shot out of 
volcanoes, and particles of carbon (soot, etc.) from chimneys; and 
(2) organic particles, such as bacteria and spores of plants. In many 
cities smoke from dwellings, factories, railroad engines, etc., consti- 
tutes one of the leading sources of atmospheric dust. Such smoke is 
largely unconsumed fuel. It is estimated that in the United States 
at least 20,000,000 tons of coal (carbon), representing a value of 
$40,000,000 or more, go up the chimneys each year in smoke. This 
enormous waste can be largely prevented, and when it is done the 
air of many great cities will be much purer than now. One of the 
most important results will be the increased comfort and improved 
health of the people living in such places. Bacteria pass with air 
into the lungs, and so reach the blood, where some of them multiply 
rapidly. Some of them cause disease, while others are harmless or 
beneficial. Many bacteria cannot endure much sunlight, and depend 



52 ELEMENTS OF GEOGRAPHY 

on dust particles for their transportation ; hence their number tends to 
be greater where there is little sunlight and an abundance of dust, as 
in great cities, especially in their crowded parts. Over the ocean, 
in the open country, and at high altitudes, on the other hand, 
bacteria are few. The number of bacteria found in a cubic meter 
of air at the Montsouris Observatory, near Paris, was 345, while 
in the same amount of air in the heart of the city the number was 
4,790. These figures give some idea of the relative purity of country 
and of city air, and explain, in large part, the health value of seashore 
and mountain resorts. Dust-free air is practically free from disease 
bacteria, hence the importance of getting rid of the dust and smoke of 
cities, as far as possible. It is claimed by some physicians that the 
impure condition of the air in cities is responsible for much criminality 
through its injurious effects on the nervous system. 

Dust particles in the atmosphere are important in several other 
ways. They scatter the light of the sun, so as to illuminate the whole 
atmosphere. Without dust in the air, all shady places would be in 
darkness. The sun would probably appear in dazzling brilliance, 
shining from a black sky, in which the stars would be visible even in 
the daytime. The blue color of the sky and the sunset and sunrise 
tints are influenced by the dust in the atmosphere. Dust particles 
also serve as centers about which water vapor condenses. In this 
way dust is an important factor in increasing the number and dura- 
tion of fogs, and the amount of cloudiness over cities where many 
fires produce large quantities of smoke. 

History and Future of the Atmosphere 

History. It is probable that the atmosphere has undergone 
changes in mass and volume in the course of its history. It was 
formerly supposed that the atmosphere was gradually becoming 
less, and that it would, in time, disappear. But this belief does not 
appear to be well founded. The atmosphere is now gaining various 
gases from volcanic and other vents (p. 301), and probably has 
always done so. It is probably getting gases from space also, and 
though the contributions from this source are small now, they may 
not always have been so. The atmosphere is losing as well as gaining. 
Some gases, especially light ones like hydrogen, probably escape the 
attractive control of the earth and pass off into space. Other con- 
stituents of the air, especially oxygen and carbon dioxide, are with- 



NATURE AND FUNCTIONS OF THE ATMOSPHERE 53 

drawn from the air, and locked up for long periods, at least, in the 
rocks. The rates both of supply and loss vary. When loss exceeds 
supply, the mass of the atmosphere must decrease; when supply 
exceeds loss, the mass must increase. It is probable that the varia- 
tions in composition have been more important than those of mass 
and volume, at least in the later part of the earth's history. 

Future. The probable future of the atmosphere is a matter of 
absorbing interest, especially because it is connected intimately with 
the question of the duration of life upon the earth. As implied 
above, there is no reason to think that the atmosphere is likely to 
disappear, to become less, or less favorable for life. The other sup- 
posed source of danger to life in general was the failure of the sun's 
heat. Its great and constant loss of heat was long thought to mean 
that its supply wo'uld soon be gone, and if the earth were not warmed 
by the sun, the temperature would be so low that such life as now 
exists could not live. But recent discoveries have revealed sources 
of great energy, heretofore unknown, in the sun, so that its heat and 
light-giving power will doubtless continue much longer than was 
once supposed. 

In the light of present knowledge, we may therefore expect the 
earth to afford conditions congenial to life through a length of time 
which passes our comprehension. This means that all the resources 
of the earth should be used wisely, for they are likely to be needed 
by endless future generations. 

Questions 

1. Enumerate the conditions (all of them) under which there would be most 
dust in the country air at a given point in northern United States. 

2. What conditions would favor an increase in the amount of dust in the air 
of cities in summer? In winter? 

3. Compare and contrast the purity of the air (1) over oceans and over lands; 
(2) in dry and moist regions; and (3) at high and low altitudes. 

4. Would you expect the average amount of C0 2 to be greater in the air of 
cities or of the open country? Why? What processes, on the other hand, tend 
to equalize the amount over country and cities? 

5. Give at least three reasons why the amount of CO2 in the air (especially 
of great cities) tends to vary in amount between summer and winter. 

6. How would the amount of nitrogen in the air probably be affected if it 
were chemically active? The amount in the earth's crust? 

7. Why do people accustomed to low altitudes breathe very much faster in 
high altitudes? 

8. Indicate various ways in which the extreme elasticity of the air favors 
human activities. 



54 ELEMENTS OF GEOGRAPHY 



References 

Davis: Elementary Meteorology. (Boston, 1894.) 

Hann: Handbook of Climatology. (New York, 1903.) 

Moore, W. L.: Descriptive Meteorology. (New York, 1910.) 

Waldo: Modem Meteorology. (New York, 1894.) 

Ward: Practical Exercises in Elementary Meteorology. (Boston, 1899.) 

The chief sources of information about the weather and climate of the United 

States are the Monthly Weather Review and the Climatological Summary, published 

by the Weather Bureau, Washington, D. C. 



CHAPTER V 
CLIMATIC FACTORS: TEMPERATURE 

General Considerations 

We have seen that the composition of the atmosphere affects life 
in important ways. Various other things connected with the atmos- 
phere, which may be called climatic factors, play important parts 
in one way or another. The chief climatic factors are (i) temperature, 
including the heating and cooling of the atmosphere; (2) moisture, 
including evaporation, clouds, and rainfall, and (3) air movements, or 
wind. 

Importance of heat. Were it not for the effect of the atmosphere 
on temperature, the heat by day and the cold by night would be 
intolerable, and the earth would be a desolate, lifeless waste. Tem- 
perature, therefore, is hardly less important than oxygen, carbon 
dioxide, and water vapor — the life-supporting elements of the air. 

The temperature which concerns land life chiefly is the temperature 
of the air in which it lives. Heat is received by the air from several 
sources, but the heat from the sun is so much greater than that 
from all other sources that it alone need be considered. That the 
atmosphere depends chiefly on the sun for its heat is shown by the 
variations in temperature from day to night, from cloudy days to 
sunny ones, and from season to season. Variations of temperature 
from time to time and from place to place are so important to all 
forms of life, including man, that it is necessary to have some easy 
way of measuring and recording them. 

Measurement of heat. Temperature is measured by the ther- 
mometer, which consists of a glass tube of uniform diameter, except 
for a bulb at the lower end. The bulb and the lower part of the tube 
are filled with some liquid, generally mercury, and this is heated until 
it boils. The boiling mercury fills the tube and expels all air, and 
while it is boiling the tube is sealed, the heat being withdrawn at the 
same moment. On cooling, the mercury contracts and fills the lower 
part of the tube only. Whenever the temperature rises, the mercury 

55 



56 



ELEMENTS OF GEOGRAPHY 



expands and rises in the tube, and when the temperature falls, the 
mercury contracts and sinks. The amount of rise or fall of the mer- 
cury shows the amount of change of temperature. 

A scale is marked on the tube so that the temperature may be read 
from it. Two scales are in common use — the Fahrenheit (F.) and 
the Centigrade (C). On the Fahrenheit scale the temperature of 
boiling water (at sea-level under normal pressure) 
is marked 212 ; on the Centigrade scale, ioo° 
(Fig. 34). The temperature of melting ^(freez- 
ing point) is marked 32 on the former scale, and 
o° (zero) on the latter. Between the freezing and 
the boiling point on the Fahrenheit scale, there 
are 180 degrees, and on the Centigrade scale 100 
degrees. It follows that i° C. is equal to i 4 A° F. 
Zero on the Fahrenheit scale is 32 below the 
freezing point, and 20 below zero Fahrenheit 
(written — 20 F.) means 52 (32 + 20 ) below 
the freezing point. The Centigrade scale is 
simpler and better than the Fahrenheit, and for 
that reason is used generally in scientific work, 
and in most European countries. The Fahren- 
heit scale is used chiefly in English-speaking 
countries, where the metric system of measure- 
ments has not been adopted as the standard. 

Records of temperatures, obtained by the use 
of the thermometer, are used in various ways. 
For the most part, however, they are used 
(1) singly, to indicate the temperature of a place at a definite time, as 
at 8 a.m., December 25; or (2) in groups, several observations 
being made at different times, and their average taken to represent 
the average temperature of a longer period. Thus from a sufficient 
number of temperature records, spread properly over a year, an 
average temperature for that year may be obtained. Similarly, 
averages for shorter periods, as seasons, months, and days, are pos- 
sible. Such averages are usually called average annual, seasonal, 
monthly and daily temperatures. The average temperature of one 
year for a given place is, as a rule, somewhat different from that of the 
preceding or following year. So also the average for a given month in 
one year may depart much from the average of the corresponding 
month in other years. Thus at St. Paul, Minn., the average January 



ocf 


C 


F 


212* 






- 














- 


- 


, 


60' 






140* 






- 








- 




20° 






65' 






- 




10* 






50" 


0° 


"= 




-32." 


'11? 






b* 



Fig. 34. Diagram 
to represent Fahren- 
heit and Centigrade 
scales. 



CLIMATIC FACTORS: TEMPERATURE 57 

temperature in 1888 was — 1° F., while in 18S9 it was 21 F. Hence 
it is customary to take the averages of a great many years to get the 
mean annual temperature, or the averages for many Januarys to get 
the mean monthly temperature for that month. The highest and 
lowest temperatures during any period are called maximum and 
minimum temperatures; the average of the highest gives mean max- 
ima, and the average of the lowest gives mean minima; the difference 
between them is the mean range of temperature. Thus there are many 
ways of using temperature observations. 

Intense cold, — 40 to — 50 F., prevails, even in mid-summer, at 
altitudes 10 miles or so above sea-level. This is known from records 
made by the use of so-called sounding balloons, which carry instru- 
ments that record the temperature of the air through which they 
rise. The warmer temperature which we enjoy at the bottom of the 
atmosphere is due chiefly to the greater absorption by jthe denser, 
lower air, of (1) sun-heat, and (2) heat radiated from land and water, 
after they have been warmed by the sun. The temperature of space 
outside the earth's atmosphere is supposed to be about — 273 C. 

(-459° F.). 

Sun heating : insolation. The northern and southern hemispheres 
receive the same amount of heat from the sun each year, but, because 
of the inclination of the earth's axis, they do not receive the same 
amounts at all seasons. In fact, they receive the same amounts 
per day only at the times of equinox. The amount of heat actually 
received by the surface of land and water is far less than the 
amount coming to the top of the atmosphere, for much is absorbed 
in passing through the air. 

(1) Other things being equal, the earth should get most heat per 
day where the sun shines the greatest number of hours. During a 
part of the summer of the northern hemisphere, latitudes above 66}4° 
have sunshine continuously (except for clouds) for more than 24 hours. 
So far as hours of sunshine are concerned, therefore, these latitudes 
should receive more heat than other parts of the earth in summer. If 
there were no atmosphere, the surface of the earth at the North Pole 
would receive, on the 21st of June, about one-third more heat during 
24 hours than the surface of an equal area at the equator, and about 
one-tenth more than an equal area in latitude 40 N. But the amount 
of heat which reaches the bottom of the air at the pole on the 21st of 
June, is materially less than that received at the bottom of the 
atmosphere in the other latitudes mentioned. 



58 



ELEMENTS OF GEOGRAPHY 




(2) Other things being equal, the surface of the land or water gets 
most heat where the sun's rays are most nearly vertical, because (a) 
the rays are there most concentrated, and (b) they pass through 
a less thickness of the air. This is shown by Fig. 35. A given 
bundle of rays, 1, falling vertically on the surface, is distributed 

^ ».^ over a given space, while an 

equal bundle of rays, 2, falling 
obliquely on the surface, is 
spread over a greater area, and 
therefore heats each part less. 
The rays oblique to the surface, 
2, have passed through a greater 
thickness of air, and more of 
their heat has been absorbed by 
it before they reach the solid 
or liquid (ocean) parts of the 
earth. These facts help to ex- 
plain why the surface at the 
pole does not get warmer than 
an equal area at the equator, 
even with months of continu- 
ous sunshine at the former place, 
and but 12 hours at a time at the latter. The snow and ice of 
polar regions prevent them from getting warm, even during the 
months when much heat is received (p. 60). 

The greater the angle of the sun's rays at any place (that is, the 
more nearly vertical they are), the greater the heat received by the 
surface at that place in any given time. The angle at which the sun's 
rays reach the earth varies from place to place, and from time to time 
at the same place, because of the inclination of the earth's axis. This 
is illustrated by Figs. 9 and 10, which have been explained. With no 
inclination of the earth's axis, the poles would receive very little heat 
from the sun at any time of year, and all places in corresponding 
latitudes in both hemispheres would always receive the same amounts 
of heat. In general, low latitudes receive the sun's rays less obliquely 
than high latitudes. In latitudes outside the tropics, slopes facing 
the equator receive the sun's rays less obliquely than horizontal 
surfaces. For this reason, the former should receive more heat 
than the latter. 



Fig. 35. Diagram to illustrate the 
unequal heating at the bottom of the 
atmosphere, due to the angle at which 
the rays of the sun reach the surface of 
the earth. The dotted line may be taken 
to represent the outer limit of the atmos- 
phere. 



CLIMATIC FACTORS: TEMPERATURE 59 

Distribution of insolation. The distribution of insolation de- 
pends on the relative position of the sun with reference to the different 
parts of the earth at different times. From Fig. 11, which has been 
studied, we see that when the sun's rays come to the earth from the 
direction W (perpendicular 2T,H° south of the equator), they are 
more oblique than at any other time in the northern hemisphere, and 
less oblique than at any other time in the southern hemisphere. At 
the same time the days are longer in the southern hemisphere than in 
the northern. Hence there are two reasons why the southern hemi- 
sphere receives more heat than the northern at this season, namely (1) 
more nearly vertical rays, and (2) more hours of sunshine. 

After the time (winter solstice, December 2 2d) when the sun's 
rays are vertical at 23^° S., they become perpendicular to the sur- 
face in latitudes farther and farther north, and on March 21st they 
are vertical at the equator. Days and nights are then equal every- 
where, because all parallels are cut into two equal parts by the circle 
of illumination (p. 19), and the sun's rays are equally oblique in 
corresponding latitudes north and south of the equator. Any latitude 
in one hemisphere is then receiving the same amount of heat as the 
corresponding latitude in the other hemisphere. This condition 
would be permanent if the axis of the earth were not inclined. 

After March 21st, the sun continues its apparent journey north- 
ward until June 21st, when its rays are vertical at the tropic of 
Cancer, 23^° N. The days of the northern hemisphere are then 
longest and the nights shortest, and the rays of the sun are then less 
oblique in this hemisphere than at any other time. At this time, 
therefore, the northern hemisphere is being heated more rapidly than 
at any other. 

From June 21st to December 2 2d, the sun appears to move so that 
its rays become vertical farther and farther south, and the preceding 
changes are reversed. 

The latitudes where the sun's rays fall vertically range from the 
tropic of Cancer to the tropic of Capricorn ; and the sun's rays are, on 
the average, least oblique between these limits. This is why low 
latitudes are, on the whole, warmer than high latitudes. 

The density of the atmosphere also affects the amount and in- 
tensity of the insolation received by the surface of the earth. Thus 
on mountains the less density of the air means more intense sunlight, 
and a greater amount of heat per unit of land surface, than is received 



6o 



ELEMENTS OF GEOGRAPHY 



at sea-level (p. 62). One effect of this is seen in the rapid growth of 
plants on mountains in early summer. 

Distribution of temperature. The temperature of one place is 
not necessarily higher than that of another because it receives more 
heat. No amount of heat, for example, would make Greenland 
warm until after the snow and ice were melted. The region about the 
North Pole does not get very warm, even when it receives much heat, 
because much of the heat received is expended in melting ice and in 
warming ice-cold water, which is warmed very slowly, and flows away 
as soon as the heating is well begun. Mountain tops are also gen- 
erally cold in spite of the great intensity of insolation there. 

After the heat from the sun has been received by the earth, it is 
redistributed to some extent, with the general result that the parts 
which get more by insolation share their heat with the parts which 
get less. The distribution of actual temperature, therefore, differs 
much from the simple distribution which insolation would give. 

There are three ways in which the air receives, loses, and transfers 
heat. These are radiation, conduction, and convection. 

(1) Radiation. The sun always radiates heat, and the surface 
which its rays strike is warmed by absorption of the radiated heat. 
A body need not be glowing hot, like the sun, or like fire, to radiate 
heat. The radiators in » our houses radiate heat when they contain 
hot water or steam. The body which radiates heat is itself cooled. 
Thus a hot piece of iron soon cools in the air, because it radiates its 



Midnight 
12 2 



Noon 
10 12 



6 8 



Midnight 
10 12 















of 












<3 


/4 


< e 


"Se k 


*»N^ 




:>fl\ 





Fig. 36. Diagram showing curves of insolation and radiation. The maximum 
temperature of the day occurs near the higher crossing, the minimum temperature 
of the day near the lower crossing. 

heat. The land warmed by the absorption of heat radiated from the 
sun during the day is cooled by the radiation of its absorbed heat 
during the night. The absorption of heat by day and its loss by 
radiation at night (Fig. 36) give variations of temperature between day 
and night. If the day is long and the night short, absorption of heat 
from the sun by day exceeds radiation by night ; and the land tends to 



CLIMATIC FACTORS: TEMPERATURE 61 

become warmer, as in spring and early summer. If the day is short 
and the night long, radiation of heat will be greater than absorption, 
and the land will become colder, as in autumn and early winter. 
When land radiates more heat by night than it receives by day, the 
excess radiated is that which was stored up in the soil, rocks, and 
waters, in the warm season. The temperature of the land, therefore, 
is largely a matter of the balance between gain of heat by insolation 
during the day, and loss of heat by radiation at night. 

(2) Conduction. If one end of an iron poker is put in the fire, the 
other end becomes hot. The heat seems to pass from one end to the 
other. This method of passing heat along is conduction. Any cold 
body in contact with a hot body is warmed by conduction. The 
hand is warmed by conduction when placed on metal or wood which 
feels warm; it is cooled by conduction if the metal or wood feels cool. 
The bottom of the air is warmed by contact with the land (that is, by 
conduction) wherever the temperature of the land is higher than that 
of the air. Conduction from the land to the bottom air is an im- 
portant factor in determining the temperature of the air just above 
the ground. 

(3) Convection. When a kettle of water is placed on a hot stove, 
the water in the bottom is heated by conduction, that is, by contact 
with the hot kettle. The heating of the water causes it to expand, 
and when the water in the bottom of the kettle expands it becomes 
lighter than the water above. The heavier water above then sinks 
and pushes the lighter water below up to the top. This sort of 
movement is convection. Another illustration of convection is afforded 
by stoves, fireplaces, and furnaces. A thin sheet of light paper may 
be held up for a moment by the rising air over a hot stove, or even 
carried -up if the convection current is strong enough. Again, as the 
air in a chimney is heated, it expands and becomes less dense than 
the air about it. The cooler, denser air about the base of the chimney 
or stove crowds in below the expanded air in the chimney, and pushes 
it up out of the chimney. Since the air entering the chimney from 
below is being heated and expanded all the time, the up-draught con- 
tinues as long as there is fire. Every draught from a chimney is an 
example of convection. 

When the surface of the land is heated by the absorption of heat 
from the sun, it warms the air above both by conduction and by 
radiation. The lands of low latitudes are heated more than 
others. The heated air over the heated land expands and rises. 



62 



ELEMENTS OF GEOGRAPHY 




Fig. 37. The first rise of air, as a 
result of heating, is due to the expansion 
of the part heated. 




Fig. 38. The permanent heating of 
the air over a region gives rise to per- 
manent convection currents. 



If the air in a given region were expanded as shown in Fig. 37, the air 
at the top of the expanded column would flow away, much as water 
would under similar conditions. After this takes place, the amount 

of air at the base of the column 
h will be less than the amount 
at the same level outside the 
heated area, and air from out- 
side the heated column will 
flow in. This inflow will push 
up the column of expanded 
air, and further overflow above 
will cause further inflow below. 
If the heating continues, a per- 
manent convection current is 
established in the heated area 
(Fig. 38). Such convectional 
movements in the atmosphere 
are important factors not only 
in distributing temperature, but also in causing winds, clouds, and 
storms, as we shall see. The summer whirlwind is an example of one 
kind of convectional movement due to heating of the land and the air 
above it. 

The atmosphere is heated (1) by the absorption of the sun's rays 
as they come through it, (2) by the absorption of heat radiated from 
land and water, and (3) by conduction from warm land or water to 
the lower air. The amount of heat absorbed by air from the direct 
rays of the sun depends on the distance the rays travel in it, that is, 
on the obliquity of the sun's rays (Fig. 35). When the sun is vertical 
at the equator, the sun's rays pass through about twice as much 
atmosphere in latitude 6o°, nearly three times as much in latitude 
70 , and about ten times as much in latitude 85 , as they do in latitude 
o°. The amount of absorption of sun-heat by the air, therefore, 
varies with latitude. About half of it is absorbed by the air at the 
equator, and about four-fifths at the poles, as compared with the 
total amount which would reach the earth in those latitudes if there 
were no atmosphere. In general, the amount of heat absorbed by the 
atmosphere may be taken as exceeding 50 per cent of the total amount 
coming to the earth from the sun. 

The heat radiated into the air from below is absorbed by the air 
more readily than that coming from the sun directly. The lower 



CLIMATIC FACTORS: TEMPERATURE 63 

air is therefore heated by radiation from below more than by direct 
insolation. 

After heat is received from the sun, therefore, it is redistributed, 
and the redistribution affects the temperature of the air. The 
redistribution is accomplished not only by radiation, conduction, and 
convection, but also by movements of air (winds) and movements of 
water (especially ocean currents). Without these movements of air 
and water, the average temperature of the equator would be much 
(perhaps 50 F.) higher than now, and that of the poles much (ioo° F. 
or more, estimated) lower than now. These changes would be 
destructive to many existing forms of life. 

Temperature of land and water. Land is heated by insolation 
four or five times as fast as water, for several reasons: 

(1) A given amount of heat raises the temperature of soil and 
rock more than that of water. 

(2) Water is a good reflector, while land is not ; the latter, therefore, 
absorbs a larger proportion of the heat of the sun's rays. The amount 
of heat reflected from a water surface increases with increasing 
obliqueness of the sun's rays. The major part of insolation on water 
bodies in high latitudes is lost by reflection. At the equator, for 
example, 40 per cent of the insolation goes into heating the water; in 
latitude 6o°, less than 5 per cent is so used. Places so situated as to 
receive this reflected heat (as south-facing slopes on the north side 
of a water body in middle latitudes of the northern hemisphere) 
have their temperature materially increased. A familiar result of 
the reflection of heat from water appears in the intensity of sun-burn 
received on water. Snow-covered land and bare white sand reflect 
heat much as water does. 

(3) Land radiates heat more readily than water does. 

(4) Convection movements are established in water as soon as 
its surface is heated. This prevents excessive heating at any one 
point. The land, on the other hand, being solid, is without move- 
ments of convection. 

(5) There is more evaporation from a water surface than from a 
land surface, other conditions being the same, and evaporation cools 
the surface from which it takes place. A wet soil, receiving the same 
amount of the sun's rays, remains cooler than a dry soil. The hot 
sand of the desert and of the sea beach is an example of this effect on 
the warming of the land. 

(6) Light and heat rays penetrate water, but not soil and rock 



64 ELEMENTS OF GEOGRAPHY 

to any great extent. The heat of insolation is therefore distributed, 
at the outset, through a greater thickness of water than of soil. 
Being confined to the surface of the latter, its temperature is made 
higher. 

Since the temperature of air tends to be the same as that of the 
surface on which it lies, the presence of land or water is an important 
factor in determining the temperature of the air above. 

Seasons 
In Middle Latitudes 

We are now prepared to understand the seasons, and the reasons 
for their differences of temperature. In middle latitudes, the seasons 
are four — spring, summer, autumn, and winter. Each season has 
characteristics of its own, but each grades into the one which follows. 

In the United States, March, April, and May are commonly 
called the spring months; June, July, and August the summer months; 
September, October, and November the autumn months; and Decem- 
ber, January, and February the winter months. In the southern 
hemisphere, spring comes in September, October, and November; 
summer in December, January, and February, and so on. The 
vernal equinox of the northern hemisphere is the autumnal equinox 
of the southern, and the summer solstice of the northern is the winter 
solstice of the southern. The definition of the seasons given above is 
based on temperature, the warmest three months being summer, and 
the coldest three, winter. 

The seasons are sometimes defined in a different way. Thus 
spring is sometimes regarded as the time between the vernal equinox 
and the summer solstice; summer the time from the summer solstice 
to the autumnal equinox, etc. 

Summer and winter temperatures. The summer (June to 
August) heat of middle latitudes in the northern hemisphere is due 
(i) to the high altitude of the sun above the horizon, giving less 
oblique rays with a shorter path through the atmosphere, and (2) to 
the long days and short nights. During the long day, more heat 
is received than is lost during the short night. The reverse of these 
conditions accounts for the low temperatures of winter, though the 
earth is then actually 3,000,000 miles nearer the sun than in summer. 
A consideration of the position of the sun with reference to places in 
the southern hemisphere (Figs. 4 and 10) will make it clear why 



CLIMATIC FACTORS: TEMPERATURE 65 

summer there occurs at the time of the northern winter. One result 
of this difference of seasons in opposite hemispheres at the same time 
is that crops in the middle latitudes of the southern hemisphere are 
harvested in our late winter and early spring, when the northern 
supplies of certain things are running low. Hence there is important 
trade between the two hemispheres, places in each hemisphere being 
benefited because their crops ripen in the off season of the other. 

The seasons in middle latitudes of the southern hemisphere are 
milder than those of similar latitudes in the northern hemisphere. 
Thus snow is very rare at Buenos Aires, Lat. 34 36' S., while at 
Wilmington, N. C, Lat. 34° 15' N., an average of 1 inch falls every 
winter. The difference is due mainly to the greater proportion of 
water in the southern hemisphere. The extent of this effect is 
suggested by a comparison of temperatures, as follows: 

Midwinter Month. Midsummer Month 

Buenos Aires (July) 50° F. (Jan.) 75 F. 

Wilmington (Jan.) 45 F. (July) 8o° F. 

Warmest and coldest months. Since the northern hemisphere 
receives its largest amount of heat at the time of the summer solstice, 
and its smallest amount at the time of the winter solstice, it would 
seem at first that these dates, respectively, should be the times of 
highest and lowest temperatures; but this is not the case. Again, 
since corresponding latitudes in the two hemispheres are being 
heated equally at the time of the equinoxes, it would seem, at first, 
that these latitudes in the two hemispheres should have the same 
temperature at these times; but this, again, is not the case. In our 
own latitudes, for example, March 21st (vernal equinox) is much 
colder than September 2 2d (autumnal equinox). 

The explanation of these conditions is found in the fact that 
the temperature of any given place at any given time is not dependent 
entirely on the amount of heat received from the sun at that time. 
In our latitudes, the surface becomes warmed during the summer, 
when the heat received during the long days is greater than that 
lost during the short nights. At the end of summer, therefore, the 
soil, rocks, lakes, and rivers have all been warmed. Heat has been 
stored up in them. At this time of year, therefore, the northern 
hemisphere has a temperature higher than that which it would have if 
it depended entirely on the heat received from the sun each day. On 
the other hand, the temperature at the time of early spring is lower 
than that which the daily heating would seem to produce, because 



66 ELEMENTS OF GEOGRAPHY 

the cold of the winter just past has not been altogether overcome. 
Some of the snow and some of the ice of lakes, ponds, streams, and 
soils, in middle and high latitudes, is still unmelted. The snow and 
ice keep the lower part of the air cool. 

For similar reasons, the summer solstice is not the hottest time 
of the year in the northern hemisphere, for the summer's heat has not 
yet altogether overcome the effect of the preceding winter. The 
time of greatest heat lags behind the time of greatest heating. In 
middle latitudes the lag is about a month; but it is more over oceans 
than over lands, because land is heated and cooled more readily than 
water. For this reason places near bodies of water usually have 
later and colder springs than places not so situated. Under such 
conditions, April may be as cold as November. For a similar reason, 
the time of greatest cold does not come till after the time of least 
heating. 

In Tropical Latitudes 

The seasons in low latitudes are unlike our own. At the equator, 
the sun's rays are vertical twice each year — at the times of the 
equinoxes. Twice a year, too, the sun's rays are vertical 23^° from 
the equator, once to the north and once to the south. The equator, 
therefore, has two seasons, occurring at the time of our spring and 
autumn, which are somewhat warmer than two other seasons 
occurring at the time of our summer and winter. The variations 
in temperature are much less than in our own latitude, for the 
length of day and night never varies at the equator, and varies 
relatively little in any part of the tropics. The angle of the sun's 
rays, too, varies less than with us. At the equator, therefore, there 
is a fourfold division of the year, but their differences of tempera- 
ture are slight. In some places the warmest month is no more than 
2 — 3 F. warmer than the coolest. Hence any seasonal division on 
the basis of temperature is unimportant. In the equatorial region, 
differences of temperature between day and night are greater, as a 
rule, than differences between the warmest and the coolest month. 
Differences in moisture perhaps offer a better basis than differences 
in temperature for a division of the year into seasons. Where wet 
seasons alternate with dry ones, the effect on life from season to 
season is great. 

In High Latitudes 

In high latitudes, the seasons are still different. About latitude 
6o°, for example, the differences in the seasons are similar to those 



CLIMATIC FACTORS: TEMPERATURE 67 

of the central part of the United States, except that they are greater, 
because of the greater variation in the length of day and night. In 
latitude 63 , the longest day of summer and the longest night of 
winter are about 20 hours each, as compared with a little over 15 
hours in latitude 40 . The long nights of winter in latitude 63 
mean much lower temperatures than in latitude 40 at that season. 
On the other hand, the long hours of sunshine in summer make 
it possible, in favored localities, to grow crops as far north as latitude 
6o°, even where it is only four months from snow to snow. 

In latitude 75 N., which may be taken as typical of polar regions, 
there are four natural divisions of the year, one (summer) when 
daylight is continuous, one (winter) when darkness is continuous, 
one (spring) when there is alternating day and night, with the days 
lengthening, and one (autumn) when there is alternating day and 
night, with the nights lengthening. The lengths of the seasons 
I defined in this way are not the same. 

There is a common notion that in polar regions there is a day of 
six months and a night of six months each year, but this is not correct. 
There is a six-month day and a six-month night at the poles only. 
In latitude 78 , about half way between the pole and the polar circle, 
there is continuous daylight and continuous darkness for periods 
of about four months each. In latitude 70 the periods of continuous 
darkness and of continuous light are two months each, and so on 
down to 24 hours at the polar circle. 

Though the name summer may be applied to portions of the year 
in high latitudes, it must be remembered that the factors controlling 
the distribution of heat and temperature do not allow places north of 
latitude 65 to become warm enough for the growth of cereal crops. 
Vegetation is confined to grasses, stunted shrubs, lichens, and moss. 
The conditions of life here are very different from those of middle 
latitudes. Hence the names of the seasons, as we use them, do not 
mean the same thing for any other than middle latitudes. 

Relation of Temperature and Altitude 

High altitudes are colder than low levels in the same region, 
(1) because the air is thinner, and (2) because it contains less water 
vapor, carbon dioxide, and dust. For these reasons it absorbs less 
heat from the direct rays of the sun, and less of that radiated from 
below. The result is that the temperature of the air at high altitudes 



68 ELEMENTS OF GEOGRAPHY 

is low, though the heat of the direct rays of the sun may be uncom- 
fortably great. Thus the air temperature on top of a mountain 
12,000 feet high may be 30 or more lower than the air temperature 
at the base, in spite of the fact that insolation is 10 to 20 per cent 
greater in the former position. 

The average decrease of temperature is about i° F. for each 330 
feet of rise, or 16 for each mile, for the altitudes where observations 
have been taken. One mile of ascent, therefore, means about the 
same decrease of temperature as a journey of 1,000 miles (about 15° 
of latitude) toward the poles. Hence tropical highlands, like those 
of Mexico or Bolivia, in latitudes 18 to 19 , N. and S. respectively, 
are really cooler than some places at sea-level in middle latitudes. 
For this reason, some countries in the tropics can produce not only 
tropical crops, but also those characteristic of other regions, and by 
living at the higher elevations, the people may escape the uncomfort- 
able heat of tropical lowlands. In middle latitudes also vegetation 
varies with the altitude. Thus, in the low mountains of Pennsylvania, 
the ridges bear coniferous trees (pines, etc.) sugar maples, and similar 
types, while the valleys between have the honey locust, gum, and 
walnut, which need a warmer climate. In the latitude of Chicago, 
corn will not, as a rule, ripen at an altitude above 2,000 feet, though 
it flourishes on lower lands. 

The low temperatures of certain mountains and high plateaus of 
the middle zones make them inhospitable, and help to condemn them 
to sparse populations. On the other hand, the cool climates of 
various upland areas in the tropics have permitted the establishment 
of permanent white settlements. During the hot summer .months 
the capital of India was transferred each year from Calcutta (capital 
until 191 1), near sea-level, to Simla in the Himalayas, at an eleva- 
tion of 7,000 feet. Certain elevated places in the Philippines, like 
Baguio, the summer capital, will have increasing importance as 
health and pleasure resorts during the hot period. 

A land surface at a high altitude may be heated more by the sun 
than one at a low altitude, and it then heats the air above it; but 
since the air over the high land is thin, it is heated less and does 
not hold the heat so well as denser air would. The result is 
that both land and air cool faster in high altitudes than in low ones, 
and this makes their average temperature less. The temperature of 
the air over land 10,000 feet high is warmer than the temperature of 
the air 10,000 feet above low land. 




CLIMATIC FACTORS: TEMPERATURE 69 

Isolated elevations like mountain-tops are colder than plateaus 
of the same elevation, because they are so well exposed to cooling. 
On clear days in summer, the sunny side of a mountain free from snow 
gets very warm (Fig. 39). If 
the rock is bare, it may become ^ N -^ 

so hot that the hand cannot be 
held on it. If the air remained 
long in contact with such a rock 
surface, it would be warmed to 
the same temperature; but it is 
commonly moved on quickly Fig. 39. Diagram to show that the 

by winds before it gets very sun's rays may fall less obliquely on a 
warm, and its place is taken mountain slope than on a plain adjacent, 
by colder air. Again, an iso- 
lated mountain-peak radiates heat in all directions except down- 
ward, while a flat surface radiates it upward only. These are some 
of the reasons why a volcanic mountain, like Cayambe, in Ecuador, 
directly on the equator, with an altitude of less than 20,000 feet, has 
its summit covered with perpetual snow, even though its altitude 
entitles it to the temperature of a place near sea-level in latitude 58 . 
Cereal crops are grown in Norway even north of latitude 5S . In 
mountains, too, there are likely to be many days when clouds shield 
the rocks from the sun. This tends to reduce the average temperature 
of the mountain, as compared with that of low land. 

The difference in vegetation and in human conditions between 
the sunny and shady slopes of mountains is striking in many cases. 
Thus at various places in high latitudes there is a great contrast 
between the scattered, feeble vegetation of the lowlands, and the 
denser, more luxuriant growth on the sunny slopes of neighboring 
mountains. Fig. 39 suggests the reason for the difference. The 
sun's rays strike the surface of the plain much more obliquely than 
they do the side of the mountain, and their heating power is therefore 
less in the former place. At a place near Zermatt, in the Alps, 
barley and rye are grown on a sunny southern slope 6,900 feet above 
sea-level, while a few hundred yards away, northern slopes, even 
below the level of the grain fields, have arctic-alpine vegetation and 
snow-banks. In some of the valleys in the Alps, most of the people 
live on the sunny slopes, and those on the shady sides are in general 
less prosperous. These differences have developed in some places 
where the advantages, apart from insolation, are identical. 



70 ELEMENTS OF GEOGRAPHY 

Where mountains are covered by snow throughout the year, 
their surfaces are never warmed above a temperature of J2° F., the! 
melting temperature of snow. All the heat received beyond that 
necessary to raise them to this temperature, is spent in melting and 
evaporating snow, not in- raising the temperature of its surface. Yet 
in spite of the freezing temperature, travellers over the snow-fields 
may be sun-burned, as if exposed to mid-summer sun at lower alti- 
tudes. Part of this effect is due to the greater intensity of insolation 
at higher altitudes, and part of it to the fact that snow reflects heat 
much as water does (p. 63). 



Representation of Temperature on Maps 

The importance of temperature and its changes makes it desirable 
to have some means by which conditions in different places and at 
different times may be readily studied. Tables of figures may be 
used if only a few places are to be compared, but for large areas it 
is more convenient to have the temperatures shown on maps. Maps 
showing temperatures are thermal maps. On such maps tempera- 
tures and their distribution are commonly shown by lines, each of 
which connects points having the same temperature. Such lines 
are isotherms, and maps showing isotherms are isothermal maps. A 
line connecting places having the same average annual temperature 
is an annual isotherm. Lines connecting places of the same average 
seasonal or monthly temperature are seasonal or monthly isotherms. 
An isothermal map should always show whether the isotherms are 
annual, seasonal, or monthly. 

Fig. 40 shows annual isotherms for each 20 F. The map does 
not give exact average temperatures for places between the lines, 
but temperatures for such places can be estimated from the maps. 
At the extreme north there is the isotherm of o° F., which lies north of 
Europe and Asia, and barely touches North America. The average 
annual temperature of places on this line is o° F. The isotherm of io° 
F. lies south of the isotherm of o° F. The average temperature of 
places between these two lines is more than o°, and less than io°. 
South of the isotherm of io° follow, in order, the isotherms of 30 , 50 , 
6o°, and 70 . The lowest isotherm shown on the chart in the south- 
ern hemisphere is that of 30 , lying south of all lands except Antarctica. 
The latitude of this isotherm corresponds nearly to the latitude of 
the isotherm of 30 in the northern hemisphere. Next north (toward 



CLIMATIC FACTORS: TEMPERATURE 



7i 




< 



72 ELEMENTS OF GEOGRAPHY 

the equator) of the southern isotherm of 30 is the isotherm of 50 , 
followed by those of 6o° and 70 . Thus the map shows the relation 
between latitude and annual temperatures, the highest temperatures 
being near the equator. 

Annual isotherms do not show all we may want to know about 
the temperature conditions of a place. An annual isotherm of 50 F., 
for example, does not tell us whether the temperature is about 50 F. 
all the time, or whether it is 8o° F. in summer and 20 in winter. 
Seasonal and monthly isotherms are of more significance in con- 
nection with crops, and give a better idea of the temperature condi- 
tions of a place. This may be illustrated by the fact that the annual 
isotherm of New York is about the same as that of southern England, 
while the summer isotherm of the former place is more than io° 
warmer than that of the latter. Since summer temperatures are the 
most important for crops and for some human activities, the difference 
of more than io° in that season is enough to make New York and 
southeastern England quite unlike in many respects. Again, San 
Francisco and St. Louis have the same mean annual temperature; 
but the January average is io° from the July average at San Francisco, 
and 45 from it at St. Louis. Range of temperature is, therefore, im- 
portant. The annual range of temperature for Quito, Ecuador, is i° 
F.; that is, the warmest month is only about i° warmer than the 
coolest. For San Diego, Cal., the range is 15 F.; for St. Paul, Minn., 
6o°; for Yakutsk, northeastern Siberia, ioo°. 

Fig. 41 shows the isotherms for January. On this chart corres- 
ponding isotherms are farther south than on the chart of annual 
isotherms. Thus the isotherm of o° F. ( — 17.78 C.) in the northern 
hemisphere runs through central Asia, instead of lying north of it, 
and the isotherm of 6o° is everywhere south of latitude 40 , instead 
of being partly north of it, as in Fig. 40. At this time of the year, 
the sun is shining vertically south of the equator. This seems to be 
a sufficient reason for the change. 

Fig. 42 shows the isotherms for July. All isotherms are farther 
north than the corresponding ones on either of the other charts. Thus 
the isotherm of 50 in the northern hemisphere is about where the 
isotherm of 20 was in January (Fig. 41). 

Comparing Figs. 41 and 42, it is seen that the difference of tem- 
perature between January and July is much greater in high latitudes 
than in low. Thus in the southern part of Hudson Bay there is 70 
difference between January and July; at Lake Erie, about 45 ; in 



CLIMATIC FACTORS: TEMPERATURE 



73 




fe 



74 



ELEMENTS OF GEOGRAPHY 




< 



to 



CLIMATIC FACTORS: TEMPERATURE 75 

Florida, about 20 ; and near the equator in South America, less than 
io°. The same charts show that the difference is greater in the 
interiors of continents than on coasts or over the sea in the same 
latitude. Thus in the interior of North America, west of Hudson 
Bay, the difference is about 8o°, while on the coast of Alaska it is 
only about 30 . These conditions bear out the conclusions already 
reached, (1) that the difference in the amounts of heat received at 
different seasons is greater in high latitudes than in low latitudes, and 
(2) that land heats and cools more readily than water. 

The line of highest temperature about the earth is the thermal 
equator. The thermal equator does not follow a straight course 
around the earth, and its position shifts with the seasons. Most 
of the year, however, it is a little north of the geographic equator, 
due to the fact that there is more land north of the equator than 
south of it, and to the further fact that land is heated more than 
water (p. 63). 

The courses of isotherms. (1) The courses of the isotherms 
are, in a general way, east-west; that is, they are roughly parallel 
to the parallels of latitude. Some of them are very irregular, it 
is true, but the east-west direction is the most common one. This 
shows some relation between the courses of isotherms and latitude; 
but since the isotherms do not follow the parallels exactly, it is clear 
that latitude is not the only thing which determines their position. 

(2) Figs. 41 and 42 show that the isotherms are least crooked 
where there is little land, and most crooked where there is much land. 
This suggests that the land and water have something to do with 
their positions. There are various irregularities in the isotherms on 
land that do not appear on the sea. Thus, on the January chart, 
there is an area in South Africa, and another in Australia, surrounded 
by the isotherm of 90 , and there are similar areas in North America, 
northern Africa, and southern Asia, in July. All of these areas are 
on land. These facts tend to confirm the conclusion that the sea 
and the land influence the position of the isotherms. 

Following this idea still further, it is seen that some of the 
isotherms of January bend somewhat abruptly toward the equator 
in passing from water to land, and toward the pole in passing from 
land to water. Thus the isotherm of 30 in the northern hemisphere 
turns to the south where it reaches North America, and again on the 
coast of Europe. In the southern hemisphere, the isotherms of 8o° 
and 70 make abrupt turns at the west coast of Africa, and the 



7 6 ELEMENTS OF GEOGRAPHY 

isotherm of 70 near the west coast of South America. These bends 
at the coasts give further support to the conclusion that the distribu- 
tion of land and water has something to do with the position of 
isotherms. 

It has been noted already (p. 63) that the land is heated and 
cooled more readily than the sea, and is therefore colder in winter 
and warmer in summer. The January isotherm of 30 in the northern 
hemisphere bends toward the equator in crossing the northern con- 
tinents, because the land is cooler than the water in the same 
latitude, at this time of year. In the southern hemisphere, on the 
other hand, where it is summer, the isotherms bend toward the pole 
on reaching the land, because the land is warmer than the sea in the 
same latitude. 

The chart of the July isotherms leads to the same conclusion. 
On this chart the isotherms crossing the northern continents bend 
poleward on the land, while those crossing the southern continents 
bend equatorward. This is the season when the lands of the northern 
hemisphere are warmer than the seas of the same latitude, and when 
the lands of the southern hemisphere are cooler than the seas about 
them. 

The irregularities of the isotherms of the northern hemisphere 
in July are much greater than those of the southern hemisphere 
in January (summer in the southern hemisphere). This is prob- 
ably because there is much more land in the northern hemisphere 
than in the southern, and the larger land areas have a greater effect 
on the isotherms than the smaller ones. 

(3) There are some features of the isothermal lines which are 
not explained by latitude, or by the distribution of continents and 
oceans. Thus the bends of the isotherms are not as pronounced on 
the east sides of the continents as on the west. This is shown by 
Figs. 41 and 42. Again, traced eastward, the January isotherm of 
40 bends southward near the west coast of North America on the 
land, while on the eastern side of the continent it bends northward 
on the sea, not on the land. Such peculiarities may be explained by 
the winds. The prevailing winds in the middle latitudes of North 
America are from the west. These winds tend to carry the tempera- 
ture of the sea (warmer in winter) over to the land on the western 
side of the continent (Fig. 41), and the temperature of the land 
(cooler in winter) over to the sea, on its eastern side. This explains 
the bends of the isotherm of 40 , for example, near the coasts in the 






CLIMATIC FACTORS: TEMPERATURE 77 

northern hemisphere in January. Coastal lands on the western sides 
of continents in middle latitudes tend to have temperatures like 
those of the neighboring ocean, and the extent to which this influence 
is felt over the land depends on the strength of the wind and on the 
topography. 

(4) The great bend in the January isotherm of 30 in the North 
Atlantic is due to a northeastward movement of warm ocean water 
in the direction of the pronounced loop of the isotherm. Ocean 
currents are therefore a fourth cause of the irregularities of isotherms. 
The amount of heat carried northward by the ocean currents of 
the Atlantic and Pacific is very large. It has been estimated that 
the temperature of the British Isles and Norway is raised several 
degrees by the warm poleward movement of waters in the North 
Atlantic. The temperature of the land is raised by this water, 
because the air over the warm ocean water is warmed and then 
blown over the land. 

The milder climate of northwestern Europe, as compared with 
northeastern North America, is not due wholly to the northward 
movement of warm water. Even without such movement, the 
climate of northwestern Europe would be somewhat warmer in 
winter than that of northeastern North America in the same latitudes. 
This is because the ocean, from which the winds of winter blow to 
northwestern Europe, still would be warmer than interior North 
America, whence the prevailing winds blow to the eastern coast of 
that continent. 

There are some other less important causes of irregularities in 
the isotherms. Thus a basin region, shut in by mountains, gets 
hotter in summer than a region not so surrounded. Again, there 
is less evaporation from a dry surface than from a moist one, and 
since evaporation cools the surface, a dry surface will be warmer 
than a moist one, if other conditions are the same. The color of the 
soil, the presence or absence of vegetation, etc., also affect the absorp- 
tion and radiation of heat. The high temperature (90 and above) 
in the southwestern part of the United States in July (Fig. 42) is 
accounted for partly by the fact that the region is somewhat shut in 
by mountains, and has a dry, sandy soil but scantily covered with 
vegetation. 

Altitude affects temperature, as already explained, but isother- 
mal charts show no relation between isothermal lines and surface 
relief. The reason is that isothermal lines are represented on maps 



7 8 ELEMENTS OF GEOGRAPHY 

as if they were at sea-level. This is done by making allowance for 
altitude at the average rate of i° F. for about 330 feet. Thus if 
the temperature of a place at an altitude of 3,300 feet is 6o°, it is 
put down on the chart as 70° (6o°+io°). Isothermal charts, there- 
fore, are intended to show the temperature as it would be if the land 
were at sea-level. 

Ranges of Temperature 

Daily range. The temperature of a day when the sun shines is 
generally warmer than the temperature of the night. The difference 
is as much as 40 or 50 F. in many places, and as much as 70 in 
some. The daily range of temperature of air over the ocean is much 
less than over the land. 

Questions: Were other things equal, would the daily range of temperature be 
greater (1) in high or low latitudes? (2) In high or low altitudes? (3) In moist 
or dry regions? (4) Where the surface is covered with vegetation or free from it? 
(5) Where the soil is light or dark colored? (6) Near the sea or far from it? Reasons 
in each case. 

The daily range of temperature is a factor in the breaking up of 
rocks to form soil, but its greatest importance is in connection with 
the growth of most crops. Since many plants, including many food 
plants, are injured or killed by a freezing temperature (commonly 
called "frost"), they are restricted to regions where the temperature 
during the growing season does not fall to 32 F. at night. Hence 
to the farmer and fruit grower a freezing temperature is one of the 
most important things connected with atmospheric conditions. The 
danger of "frost" at night varies with local conditions, as (1) altitude, 
(2) exposure, (3) character of the soil, and (4) nearness to water 
bodies. Valley bottoms have frosts earlier in the autumn than 
neighboring hillsides, because the colder, heavier air moves down 
slopes and accumulates in low places. The great coffee plantations 
of Sao Paulo, Brazil, the olive and fig trees of Italy and Istria, the 
orange and peach orchards of California, and the vineyards in the 
Rhine Valley and in the south of France are found largely on hill- 
sides. Locally, parts of a hillside are essentially free from frost. 
Such areas are called "frostless belts." Polk and Macon counties 
in North Carolina possess such belts, which are there used for growing 
special kinds of grapes. The Polk County belt lies at an altitude of 
about 1,500 feet, and extends for about 8 miles along the mountain 
side. In some of the fruit-raising valleys of the Northwest, it is 



CLIMATIC FACTORS: TEMPERATURE 79 

customary to speak of the " frost line," that is, the line on the slopes 
below which frost is likely to be destructive. 

Northern slopes are more subject to frosts than are southern 
slopes, because the latter are warmed more by day and hence must 
cool more at night before a freezing temperature is reached. Sandy 
soils are more liable to frost than clay soils situated similarly, for 
the reason that clay soils are usually wetter. The air above them 
contains more moisture, and so cools less readily. The condensation 
of moisture sets free heat and so checks further cooling. Of two 
perishable crops on the same farm, one on clay soil, the other on 
sandy soil, the one may be untouched by "frost" on a night when 
the other is seriously injured. Moisture in the soil is always con- 
sidered in making frost predictions. Localities near water bodies, 
and in their lee (i.e., on the side toward which the wind blows from 
the water), have their temperatures influenced by the temperature 
of the water. Hence rapid cooling at night in the autumn is some- 
what less likely in such situations, and frosts are held off. The 
value of this relation is found in the location of important fruit 
districts on the lee (east) shore of Lake Michigan, and on the lee 
(southeast) shores of Lakes Erie and Ontario. A similar influence 
affects the important fruit and trucking industry of the peninsula 
between Delaware and Chesapeake bays. 

Frost prediction. The probability of frost occurrence, for any 
night can be predicted with much accuracy from the relation known 
to exist between (1) the temperature of the air, (2) its relative 
humidity, and (3) the amount of cooling necessary to reach the dew 
point. 

Calculation of the dew point is made with an instrument known as the psy- 
chrometer, consisting of two thermometers mounted in such a way that they may 
be whirled rapidly in the air. One thermometer, of the ordinary type, is known as 
the dry bulb thermometer, the other, with the mercury bulb surrounded by a 
wet wick, is the wet bulb thermometer. As the instrument is whirled, evaporation 
from the wick causes the temperature of the wet bulb thermometer to fall below 
that of the dry bulb. The difference between the two readings and the temperature 
of the dry bulb (air temperature) is then referred to tables known as dew point 
tables, from which the temperature of the dew point for air of that temperature 
and humidity is determined. If this dew point temperature lies near to 32 F., 
and conditions are favorable for rapid radiation, frost occurrence is probable. 
Equipped with a psychrometer and dew point tables, anyone can make satisfac- 
tory observations on the probability of frost. 

The economic importance of frost is so great that the federal 
government has given much attention to methods for protecting 



80 ELEMENTS OF GEOGRAPHY 

perishable crops, and one of the most valuable services of the Weather 
Bureau is the sending out of frost warnings which give the farmers 
of the country anywhere from 6 to 24 hours to make preparation 
for protection. In this way, millions of dollars' worth of crops are 
saved every year. The cost of protection for several consecutive 
nights may not equal 1 per cent of the value of the crop saved. 

Other effects of daily changes. The average daytime tempera- 
ture during the growing season, and the number of days when the 
temperature is above a given point, are also important, since most 
plants require a temperature well above 32 F. 

The daily range of temperature is also important to human beings, 
especially where the days are hot. Thus in desert regions the heat 
of midday may be much above ioo° F.; but night temperatures in 
the same place may be as low as 45 or 50 F., making restful sleep 
possible. A station in the Sahara and one at Manila afford ex- 
amples of difference of daily range. 

Max. Min. 

Daily mean. Day temp. Night temp. Range. 

Southern Tripoli 87 ° 106 ° 62 ° 44 ° 

Manila 91° 96° 86° io° 

The heat in Tripoli is borne more easily than that of Manila, 
because of the relief at night in the former place. It is the daily 
range of temperature which accounts partly for the invigorating 
effects of a vacation in the mountains. Many famous Swiss health 
resorts, for example, depend for their winter popularity on the 
intensity of the sunshine by day, followed by crisp, cold nights. 

Seasonal range. The seasonal range of temperature is affected 
by (1) latitude, (2) position with reference to land and sea, (3) pre- 
vailing winds, and (4) the presence of snow. 

(1) The seasonal range of temperature increases with the latitude 
(compare Figs. 41 and 42, pp. 73 and 74), because the yearly varia- 
tion of insolation increases with the latitude. San Diego and St. 
Paul (p. 72) are examples. In latitudes higher than that of St. Paul 
the range is still greater. 

(2) Islands have a lesser range of temperature than continental 
lands in the same latitude, and coasts have a lesser range than in- 
teriors, because the range of sea temperature is less than the range 
of land temperature (Figs. 41 and 42). St. Louis and San Francisco 
(p. 72) are examples. 



CLIMATIC FACTORS: TEMPERATURE 81 

(3) A coast to which the prevailing winds blow from the ocean 
has a less range of temperature than a coast to which the prevailing 
winds blow from the land. Thus the range of temperature is less 
on the Pacific coast of the United States than on the Atlantic in the 
same latitude (Figs. 41 and 42), the winds being chiefly from the west 
in both cases. San Diego, Cal., with a range of i5°F., Yuma, Ariz., 
with 2 7 , and Savannah, Ga., with 34 , illustrate this effect. 

(4) The presence of snow during the warm season, as in high 
latitudes and high mountains, prevents a high temperature, even 
though insolation is strong (p. 70). In the cold season, snow also 
tends to reduce the temperature of the lower air by reflecting a 
certain amount of insolation which might otherwise help to warm 
the land, and so the layers of air in contact with it. On the other 
hand, snow lessens the range of temperature of the soil beneath it, 
for snow checks radiation from the soil, and prevents it from being 
warmed by the direct rays of the sun. Unfrozen ground may exist 
under a heavy covering of snow, even though the air above the snow 
is far below the freezing point. By preventing alternate freezing 
and thawing of the soil, snow is important to many plants, as, for 
example, to winter wheat and clover. 

Importance of temperature ranges. The annual range of tem- 
perature affects all industries connected with the soil. In general, the 
temperature of most importance to vegetation is the lowest or mini- 
mum temperature. For example, the palm-tree cannot grow where 
frosts occur; hence its distribution is limited to places where the lowest 
temperature of the year is above 32 F. Peach-trees, unless pro- 
tected, are injured by protracted temperatures below — 15 F.; and 
the frequent recurrence of such temperatures in winter prohibits the 
growth of peaches. For other plants, as corn, cotton, rice, tobacco, 
sugar cane, most fruits, and vegetables, the length of time without 
freezing temperatures (the growing season) is a critical factor. 

Frosts during the growing season are, in some cases, so destructive 
as to amount almost to national disasters. A frost in the late spring, 
after corn is well started, or in early autumn, before it is ripe, may 
reduce the crop of good corn by millions of bushels. When freezing 
temperatures extend into regions usually free from them, they do 
great damage to fruit, as to orange groves in Florida. A disastrous 
frost in December, 1894, affected this region. Untimely frosts 
destroy not only tender crops for that year, but in some cases for 
years to come. Thus early in October (10-12), 1906, a temperature 



82 ELEMENTS OF GEOGRAPHY 

which was in places 13 below freezing point killed hundreds of 
thousands of peach-trees in western Michigan. Peach-trees stand 
much lower temperatures in winter without injury, but this freezing 
temperature came before the trees were ready for it. A similar 
destruction of peach-trees occurred in parts of Ohio as a result of 
unseasonable cold early in December, 1910. 

The seasonal range of temperature, or, more exactly, the tempera- 
ture of winter, affects transportation. Navigation ceases early in 
winter (usually by December 15th), for example, on the Great Lakes, 
because ice forms about their borders and does not melt until after 
March 15th. Canal and river navigation amounts to little in middle 
latitudes from December to March, and many harbors, as that of 
Montreal, are blocked by ice for weeks at a time. The desire for a 
harbor free from ice in winter led the Russians to acquire Port Arthur, 
and helped to bring on the Russo-Japanese War, because Vladi- 
vostok, the port of Russia in Asia, is ice-blocked three to six months 
every winter. 

Questions 

1. From what sources, other than the sun, does the earth's surface receive 
heat? 

2. Why does the earth get only about ^sttooVoooo part of the heat radiated 
by the sun? 

3. Suggest a method of determining the actual points which are to be marked 
212 and 32° on the tube of the Fahrenheit thermometer. 

4. What temperature Centigrade corresponds to 45 F.? To — 45 F.? 

5. Make a rule for changing degrees F. to degrees C, and vice versa. 
' 6. Suggest ways of obtaining the annual temperature of a place. 

7. Enumerate the atmospheric conditions (all of them) under which most 
heat from the sun would reach the ground at a given place in the United States. 

8. Enumerate the conditions (all of them) of land surface under which most 
heat from the sun would reach the ground at a given place in the United States. 

9. The earth is probably not getting warmer, in spite of the fact that it i 
receiving heat continually from the sun. Why? 

10. On June 21st, in latitude 40 N., which would receive more heat, (1) ; 
horizontal surface, or (2) a vertical surface of equal area facing south? Which 
would receive more on December 21st? September 21st? Draw diagrams to 
illustrate answer. 

11. For each of the various ways of heating a house, by (1) open fire, (2) stoves, 
(3) hot-air furnace, (4) steam, and (5) hot water, which process of heat distribution 
(radiation, convection, conduction) is most important? 

12. In what way may satisfactory ventilation of a heated room be secured? 

13. What conditions of the atmosphere at sea-level would cause the amount of 
heat it absorbs to vary? 



CLIMATIC FACTORS: TEMPERATURE 83 

14. Why does snow mixed with dirt melt more rapidly than clean snow? 

15. How does a lake tend to modify the temperature of the surrounding 
land by day? By night? In summer? In winter? Explain each. 

16. What effect would it have on the seasons, and on the products of middle 
latitudes (say 40 ) if the earth's axis were inclined ss}4° instead of 23^°? What 
would be the effect on seasons in the tropics? 

17. Explain each important curve in the January isotherm of io° F., northern 
hemisphere (Fig. 41). 

18. (1) Compare and contrast the average January and July temperatures on 
the east and west coasts of the United States at the fortieth parallel (Figs. 41 
and 42). (2) Explain the differences. 

19. Why are the average annual temperatures over tropical lands higher than 
those over tropical seas? 

20. Where do the highest July temperatures occur (Fig. 42)? Why there? 
The lowest January temperatures (Fig. 41)? Why? 

21. Compare and contrast the seasonal range of temperature in the middle 
latitudes of the two hemispheres (Fig. 41 and 42). Why the difference? 

22. Of two cities, St. Paul and Key West, one has an average daily range in 
temperature twice as great as the other. Which has the greater? Reasons? 

23. Why is the average annual temperature higher in cities than in the sur- 
rounding country? Why is the daily range of temperature smaller in cities than 
in the country? 

24. What is the length of the growing season in mountains, as compared with 
neighboring plains? 

25. What conditions of air movement would you expect to find along the 
thermal equator? 

26. On the equator, what altitude would have an average temperature of 
32° in January? (Consult Fig. 41.) In July? (Fig. 42.) What would be the 
altitude for an average temperature of 32 in latitude 45 in January? In July? 

27. Describe the probable changes of temperature in the different seasons for 
the places whose range of temperature is given on p. 72. 

28. Why is frost less likely to occur on cloudy than on clear nights? 

29. Suggest ways of protecting crops depending on this same principle. 

30. What probably led to the early invention of the lamp by certain natives 
on the Arctic shores of North America? 



References 

Davis: Elementary Meteorology, Ch. V. (Boston, 1894.) 

Hammon: Frost: When to Expect it, and How to Lessen the Injury Therefrom; 
Bull. No. 23, U. S. Weather Bureau. 

Hann: Handbook of Climatology, Chs. I, VI, VII, XII, XIV, XV. (New York, 

1903O 

McAdie: Frost Fighting; Bull. No. 29, U. S. Weather Bureau. 

Merriam: Laws of Temperature Control of the Geographic Distribution of 
Terrestrial Animals and Plants, in Nat. Geog. Mag., Vol. VI, pp. 229-238. 

Moore, W. L.: Descriptive Meteorology, Ch. VI. (New York, 1910.) 



CHAPTER VI 
CLIMATIC FACTORS: MOISTURE 

Importance of Atmospheric Moisture 

The atmosphere always contains water vapor, even in the desert, 
where the air seems driest. We cannot see or smell or feel water 
vapor, though air with much water vapor has a different feeling from 
air with little. 

The presence of water vapor in the air may be proved in various 
ways. If a pitcher of ice-water stands in a warm room, drops of 
water may appear on the outside of it, and cold window panes often 
-have "steam" on them in winter. In each case the water came from 
the air. Water vapor often condenses into water on the surface of 
dust particles in the air. Great numbers of these water-covered 
particles high in the air form clouds, from which rain may fall if the 
drops become heavy enough. 

Water vapor is lighter than dry air; that is, a cubic foot of it 
weighs less than a cubic foot of dry air at the same temperature and 
under the same pressure. Water vapor in the air displaces some of 
the oxygen and nitrogen, and its presence therefore makes the air 
lighter. 

The moisture of the atmosphere is no less important than oxygen 
and carbon dioxide to all animals and plants, for without it no life 
could exist on the land. It furnishes the rain and the snow which 
supply all springs and rivers, and it serves a most important function 
in connection with temperature, as already indicated, for it absorbs 
heat radiated from the sun and from the earth. It increases the 
average temperature at the bottom of the atmosphere, and reduces 
the extremes of heat and cold which would exist if the air were alto- 
gether dry. Its effect on temperature is shown by the fact that dry 
regions have greater ranges of temperature than moist ones in similar 
latitudes and altitudes. Moisture from the air also acts with the 
oxygen and with changes of temperature in the weathering of rocks 
and the formation of soil from them (p. 261). 

84 



CLIMATIC FACTORS: MOISTURE 85 

Evaporation 

Sources of water vapor. Water which is left standing in 
an open dish disappears slowly, and muddy roads and wet pave- 
ments become dry after the rain ceases. The water disappears in 
the form of vapor, which is water in particles too small to be seen. 
Vapor is passing from all moist surfaces into the air all the time. 
The change of liquid water into water vapor is evaporation. Evapo- 
ration also takes place from snow and ice, even though the tempera- 
ture is far below that of melting, as shown by the slow disappearance 
of snow and ice, even when the temperature is below 32 F. Explor- 
ers in Arctic regions report that moist garments left on the snow 
during a clear night may be dry in the morning, even with a tempera- 
ture of — 40 F. The water in the garments freezes, and the ice 
evaporates. 

All animals breathe out water vapor into the atmosphere. This 
is seen in winter when the water vapor of the breath condenses, and 
so becomes visible, in the cold atmosphere. The water breathed out 
into warm air is not seen because it does not condense. Plants also 
give out moisture, the amount, in many cases, being very great. 
Thus a thrifty sunflower plant, during its life of 140 days, gave off 
125 pounds of water. Grass was found to give off its own weight 
of water every 24 hours, in hot weather. This meant, where the 
measurement was made, 6]/2 tons per acre, or a little more than a 
ton for a lot 50 feet by 150 feet. A birch-tree, with some 200,000 
leaves, was estimated to give off 700 to 900 pounds on a hot summer 
day, but much less on a cool day. Under certain conditions, wet 
ground, like wet meadow land, is made drier by planting trees which 
take up water from the soil and give it out to the air through their 
leaves. Attempts are being made in this way to improve conditions 
near Vera Cruz, Mexico. Water vapor also enters the air from all 
active volcanoes (p. 299). The oceans, however, are the great 
evaporating pans irom which most water vapor comes, and but for 
them, the waters of the land would all be dried up in the course of 
time. 

Water is in constant circulation in the air. The circuit which it 
makes is somewhat as follows: (1) It is evaporated from the ocean 
(and all moist surfaces) ; (2) as vapor, it is diffused or blown over the 
land, where some of it (3) is condensed and falls as rain or snow, 
feeding rivers, lakes, etc. A part of the rain which falls on the land 



86 ELEMENTS OF GEOGRAPHY 

returns directly to the sea through rivers, a part sinks into the soil 
and rocks, and another part is evaporated again without flowing to 
the sea. The evaporation of water and the circulation of water 
vapor in the air are therefore important, not only for man, but for 
all living things. About half the water vapor of the air is below an 
altitude of 6,500 feet, and fully three-fourths of it below an altitude 
of 13,000 feet. The greater amount of water vapor in the lower 
part of the air, is one reason why the lower air is warmer than the 
upper air (p. 67). 

On the average, 30 to 40 inches of rain fall each year on land; that 
is, enough to make a layer 30 to 40 inches in average depth if spread 
out over all the land. The amount of water evaporated from the 
oceans each year is about the same as that which falls from the air. 
If the precipitation (rainfall and snowfall) on the oceans is equal to 
that on the lands, square mile for square mile, and if all the water 
of the rain and snow came from the oceans and was not returned to 
them, the oceans would be dried up in 3,000 or 4,000 years. If an 
amount of water equal to all the rainfall of a year were evaporated 
from the lakes of the earth, they would probably be dried up in less 
than a year. 

Rate of evaporation. Fig. 43 shows the estimated amount of 
evaporation which there would be per year from surfaces of lakes in 
various parts of the United States, if such bodies of water were present. 
Thus in Mississippi, if there were no rainfall or inflow, a surface of 
water would be lowered more than 50 inches in a year by evaporation; 
at New York, about 40 inches; at Milwaukee, about 30 inches; at 
Lake Superior, about 20 inches; at Denver, about 70 inches; and in 
southern Arizona, 90 to 100 inches. The greatest evaporation in 
the United States, so far as determined, is 101 inches per year, at 
Ft. Grant, Ariz.; the least, 18 inches, at Tatoosh Island, Wash. 

By comparing these figures with the amounts of precipitation in 
different localities, it appears that the surface of a body of water 
having its level determined solely by precipitation and evaporation, 
would rise a few inches each year in Mississippi, would remain at 
about the same level at New York, and would be lowered seven 
or eight feet every year in Arizona. It is estimated that the lake 
called Salton Sea (southeastern California) will disappear by evapora- 
tion by 1925. 

Several conditions affect the rate of evaporation. The principal 
ones are (1) the amount of water vapor already in the atmosphere, 



CLIMATIC FACTORS: MOISTURE 



87 




88 ELEMENTS OF GEOGRAPHY 

(2) the temperature of the surface and the air over it, and (3) the 
strength of the wind. At a given temperature, the less the water 
vapor in the air, the more rapid the evaporation from a water surface. 
Raising the temperature of air from 30 to 50 F. doubles its capacity 
to hold water vapor, and hence increases the rate of evaporation. 
Air moving at the rate of 10 miles an hour will evaporate four times 
as much water as still air, other things being equal. 

Effect of evaporation on temperature. Evaporation cools the 
surface from which it takes place. If the hand be moistened, it feels 
cool as the water on it evaporates, and the faster the evaporation, 
the more distinct the cooling. Moist clothing seems cooler in wind 
than in still air, even when the temperature is the same, because 
wind hastens evaporation. For the same reason, a day in summer 
when the wind is blowing seems cooler than a calm day when the 
temperature is the same. It takes about 1,000 times as much heat 
to evaporate a pound of water as it would take to raise its temperature 
i° F. Evaporation from forested regions in moist tropical lands is 
so great that the temperature there is much lower than would be 
expected from the insolation. The slight evaporation from dry 
regions is one reason why they are so hot in the sunny days of sum- 
mer. On the other hand, the increased evaporation from the human 
body in a dry region may reduce its temperature enough to make the 
heat less trying. It is a common thing to speak of dry heat as less 
uncomfortable than damp heat. The hot, dry air of a furnace room 
causes far less discomfort than the less hot, damp air of a green- 
house. On the other hand, moist air at o° F. seems much cooler than 
dry air at the same temperature. 

Evaporation and sensible temperature. Atmospheric moist- 
ure and evaporation, therefore, have much to do with the temperature 
as we feel it. The difference between temperature as it seems {sensi- 
ble temperature), and temperature as it is (as shown by the thermom- 
eter) is often great. Thus observations in Death Valley, California, 
showed a maximum air temperature of 122 on five days, but the 
sensible temperatures (determined by a specially constructed instru- 
ment) ranged from 73 to 77 F. Similar observations for various 
parts of the United States show results as follows: 

Air Temp. July Sensible Temp. Difference 

Boston (moist air) 72 65° 7 

Savannah (moist air) 82 75 7 

Yuma (dry air) 92 70 22 



CLIMATIC FACTORS: MOISTURE 89 

Thus Yuma does not seem so hot in summer as Savannah, and but 
little hotter than Boston. Sensible temperatures bear a very impor- 
tant relation to sunstroke and heat prostration, both of which are 
almost unknown in our dry southwestern states, but are of frequent 
occurrence along the less hot but moister eastern coast. 

Evaporation and saturation. The amount of water vapor in 
the air varies greatly from place to place, and from time to time at 
the same place. When there is as much water vapor in the air as 
there can be under existing conditions, it is said to be saturated. 
Though we commonly say the air is saturated, yet it is, in reality, 
not the air, but the space which the air occupies which is saturated. 
The amount of water vapor necessary to saturate a given space 
depends on the temperature, and is nearly the same whether air is 
present or not. A cubic foot of air at o° F. is capable of containing 
]4. grain of water vapor; at 30 , about 2 grains; at 6o°, 5 grains; at 8o°, 
11 grains; and at 90 , nearly 15 grains. Thus the higher the tempera- 
ture the greater the amount of water vapor necessary for saturation. 
Each increase of 20 in temperature about doubles the amount of 
water vapor a given space can hold. 

Humidity 

Absolute and relative humidity. The amount of moisture 
which the air contains is its absolute humidity. The percentage of 
moisture which air contains at any temperature, compared with 
what it might contahTat that temperature, is its relative humidity. 
Thus if a cubic foot of air at 30 F. contains 2 grains of water vapor, 
it is saturated, and its relative humidity is 100 per cent. If the tem- 
perature is raised to 6o° F., its capacity for water vapor is increased 
from 2 grains to 5 grains, and it then has only two-fifths the amount 
it could hold. Its relative humidity is therefore 40 per cent. Be- 
neath such air, evaporation would take place rapidly from all moist 
surfaces, and the humidity would rise. On the other hand, if air 
at 8o° F., containing 5 grains of water vapor (relative humidity about 
46 per cent), were cooled to 6o° F., the 5 grains would mean saturation 
for that temperature. Evaporation would then cease. Hence it 
appears that humidity and evaporation are related intimately, and 
that both depend on changes of temperature. These relations are of 
particular importance in connection with dew, fog, clouds, rain, and 
snow. They are also important to all land life. 



9 o ELEMENTS OF GEOGRAPHY 

Air is said to be "dry" when its relative humidity is low, and 
"moist" when its relative humidity is high. Thus 5 grains of water 
vapor in air at 90 F. means dry air (humidity 33), while the same 
quantity of water vapor in air at 6o° F. means damp air. The air 
over damp England and that over the dry Sahara, for example, may 
have the same actual amount of water vapor per cubic foot. 

Fig. 44 shows the average relative humidities throughout the 
United States, the range being from 80 along the coasts to less than 
40 in some part of the southwest. Areas where the relative humidity 
is 35 or less are essentially desert, and areas where it is less than 50 
are distinctly dry. In Death Valley, California, one of the driest 
places on earth, the average relative humidity for five months, when 
the record was kept, was 23 ; yet this is but little less than the relative 
humidity of the air in the average furnace-heated house in winter. The 
average relative humidity of air over the land is probably about 60; 
that over the ocean about 85. In that part of the United States which 
is productive, agriculturally, without irrigation, the relative humidity 
is, as a rule, more than 65. In high altitudes, relative humidity and 
sensible temperatures are both low, as a rule. 

Importance of relative humidity. Corn, wheat, and rye, 
require, respectively, about 14, 10, and 8 inches of water during their 
growing seasons. If the total rainfall of a given place is 18 inches in 
that time, any one of the crops would seem to have enough. Prac- 
tically, however, the relative humidity (and therefore the amount 
of evaporation) determines which of these crops may be grown with 
success. If the relative humidity is very low, rye only can be grown 
successfully, even with 18 inches of rain. 

Relative humidity has important effects on the human body. The body is 
giving off moisture constantly, most of it being evaporated from the skin and 
lungs. High humidity checks evaporation, and this seems to be one cause'of cer- 
tain diseases in moist tropical regions. One such disease, anamia, accounts for 
the characteristic tropical laziness. Low humidity increases evaporation from the 
body, and this is, on the whole, stimulating. It is believed by some that the 
excitable character of the people of some dry countries is due in part to this fact. 
Sudden changes from low to high humidity, especially when associated with sudden 
changes of temperature, such as occur when one goes out from a warm house in 
winter, probably favor diseases of the breathing organs (cold, etc.), so frequent at 
that, season. 

High relative humidity hastens the decay of food, especially meat; hence 
supplies of this food cannot be kept long in warm, moist regions. This is perhaps 
one reason why meat is little used in tropical countries. Unprotected iron wares 
rust rapidly in damp air; hence shipments of such wares to many tropical countries 



CLIMATIC FACTORS: MOISTURE 



9i 




92 ELEMENTS OF GEOGRAPHY 

require special packing to prevent injury in transit. The damp air of the coast 
of Maine prevented the successful development of the sardine industry, in spite 
of a law providing that the drying should be done only on "dry clear days," until 
a special method of curing the fish made it possible to compete with the French 
product dried out of doors. Low humidity permits salt making by natural evapora- 
tion in Mediterranean countries. In some places meat is dried in the air, giving 
the so-called "jerked beef," and even "burial" of the dead may be on high plat- 
forms in regions where dry air quickly mummifies the body. 

Extreme dryness and the evaporation which goes with it cause wood to shrink, 
warp, and crack to such an extent that boxes which were strong fall apart. Goods 
to be shipped far through a very dry region need special preparation, and even 
railroad cars have to be of steel to withstand the effect of desert dryness. Humidity 
is so important in textile industries, as in spinning cotton, that the early centers 
of cotton manufacture tended to develop in damp regions. In the best mills, 
special devices are now used to maintain uniform humidity. 

Dew point. As already stated, saturation may be produced by 
cooling the air. If saturated air is cooled, some of its water vapor 
is condensed (formed into liquid). The temperature at which the 
water vapor of the air begins to condense is the dew point. Saturated 
air is therefore at the dew point. Air may be brought to the dew 
point in various ways: (i) It may be blown where the temperature 
is lower, as to a higher latitude or altitude; (2) it may be cooled by 
having cooler air brought to it, as by a cold wind; (3) it may be cooled 
by radiation, or (4) by expansion, as when it rises. 

The temperature of the dew point is not fixed, but is influenced 
by the amount of water vapor in the air, as already explained (p. 89). 
If air at 8o° F. contains 5 grains of water per cubic foot, its dew point 
will be reached when it is cooled to 6o° F. ; but if the amount of water 
vapor in air at 8o° F. is only 2 grains per cubic foot, the dew point 
would not be reached until it had been cooled to 30 F. 

If the temperature of condensation is above 32 , the vapor con- 
denses into liquid water, which at first takes the form of droplets, 
such as those of which fog is made. If the temperature of condensa- 
tion is less than 32 , particles of ice form as the vapor condenses. 
They may be the beginnings of snowflakes, or they may be particles 
of frost. The condensation of water vapor sets free an amount of 
heat equal to that absorbed in its evaporation. This heat checks 
the cooling, a fact of significance where the temperature of condensa- 
tion is near 32 F., and where continued cooling would bring the 
temperature to the freezing point. 

Dew and frost. In the clear, still nights of summer and autumn, 
the temperature of the surface of the land, cooling by radiation, 



CLIMATIC FACTORS: MOISTURE 93 

often becomes lower than the dew point of the air above. Moisture 
then condenses on the surface. Such moisture is dew if the tempera- 
ture of condensation is above 32 . The water which condenses on 
the outside of a pitcher of ice-water (p. 84) is dew, just as much as 
that which forms on grass blades. Dew does not fall, but condenses 
on the surface of solid objects. Dew is more likely to form on still 
nights than on windy ones, because wind tends to move away air 
which is approaching its dew point, supplying other air in its place, 
and the incoming air may be warmer or drier than that which moved 
on. Dew is more likely to form on clear nights than on cloudy ones, 
because radiation and cooling are greater when there are no clouds. 
This association of dew with clear skies led the ancients to believe 
that dew came from the stars. It was, therefore, thought to be 
possessed of important curative properties. When the tempera- 
ture of the dew point is below 32 F., the moisture which con- 
denses on solid objects condenses as ice particles, or frost, instead 
of dew. 

Dew, and sometimes frost, may form on the under sides of objects. If a pan 
is placed bottom up on the ground, there may be dew on the inside of it in the 
morning. There is often dew on the under side of a flat stone when there is none 
on its top. This may be true even in a desert. The explanation is as follows: 
The air in the ground has some moisture, and during the day, when the sun shines, 
this air is warmed. At night the air above cools much more quickly than that in 
the ground. The cooler, heavier air above then sinks into the ground, crowding 
up the warmer air below with its water vapor. On reaching the cool pan, or other 
object, some of the moisture is condensed. In the day-time the rising moisture 
does not condense on the pan, because the pan is warmer than the water vapor 
below, especially if the sun is shining. The water vapor in the soil also diffuses 
upward, even when not crowded up by the sinking of heavier air. It thus appears 
that part of the moisture forming dew comes from the soil. Laboratory experi- 
ments have shown that some of it comes from the vegetation itself. The mois- 
ture of the air, however, is the great source of dew. 

In most places dew is rather unimportant, because the amount of moisture so 
condensed is small. It is difficult to measure the amount of dew, partly because it 
evaporates so quickly in the morning, and partly because the color and composition 
of the object on which it accumulates play an important part in influencing the 
amount. In some places, as in certain tropical districts, the amount of dew is 
great (-jV inch per night in some cases) and serves much like a light rain in supply- 
ing moisture to vegetation. 

Fog and cloud. The condensing of water vapor in the air into 
droplets makes fog (Fig. 45) if the condensation takes place in the 
lower part of the atmosphere at a temperature above 32 F. It 
makes ice particles, or frost, if the temperature is below 32 F. The 



94 



ELEMENTS OF GEOGRAPHY 



water droplets and ice particles take the form of clouds if the conden 
sation takes place above the bottom of the atmosphere (Figs. 46-49) 
Fog and frost particles in the lower air are the same as clouds, except j 
that clouds are higher. Fog may be said to be cloud resting on the 
surface of the land. If moisture condenses and the particles remain 
suspended in the air above the top of a mountain, there is, to the 
observer on the plain or in the valley below, a cloud about the moun- 




Fig. 45. Fog over the lowlands, as seen from Mount Wilson, California. (Ellerman.) 

tain; but if the observer were to climb up into the cloud, it would 
then appear as fog. Fogs are formed in many cases where the moist 
air over warmer water (e.g., a warm ocean current) blows over a 
colder surface of water or land. The droplets of water forming fog 
and cloud are very small, many of them not more than 3-0V0 of an 
inch in diameter. Though they are always tending to sink, they are 
so small that the gentlest currents of rising air are sufficient to keep 
them up. 

Fogs often form in valleys at night (Fig. 45), especially in autumn, when the 
night temperatures are much lower than those of the day. The cooler air settles 
in the valleys, and the air there is more likely to be brought to the dew point than 
that over the uplands. Fogs occur more frequently in large cities than in the nearby 
country, apparently because the large numbers of solid particles poured into the 



CLIMATIC FACTORS: MOISTURE 95 

air in the form of smoke favor condensation. In London the increase in coal 
consumption was accompained by increased fogs until the "smoke nuisance" was 
partly stopped; then the fogs decreased. In other places, also, doing away with 
smoke has practically put an end to fogs. 

The composition of city fog may be judged from the calculation that in a year 
the amount of solid matter (mainly soot) deposited from fogs in London amounted 
to six tons per acre. A three days fog in Manchester, England, was calculated to 
deposit 150 pounds of sulphuric acid per square mile. The shutting off of sunlight 
from London by fogs probably means, for the whole city, an expense of at least 
$5,000,000 a year for extra gas. A dense fog in London, which lasted from Decem- 
ber 10 to 17, 1905, was estimated to have cost the city $1,750,000 per day, in one 
way and another, largely through suspension of business. Such estimates are, 
however, to be taken with reserve, since much of the suspended business is trans- 
acted later. City fogs are generally injurious to health, and long continued fogs 
may cause a distinct increase in the death rate. 

Fogs interfere with all kinds of traffic; they are the most common cause of 
disasters at sea, as in the collision of the French steamship La Burgogne with an 
iceberg, in the North Atlantic, as a result of which more than 600 lives were lost. 
Coastwise traffic, as in Nantucket Sound, or traffic in river harbors, as at Philadel- 
phia, is kept at a standstill for days at a time by fogs. Fogs are also a common 
cause of railway accidents. So harmful are fogs in these ways, that elaborate 
experiments have been made to dispel them in railway yards and in front of vessels. 
Various devices, using heated air to evaporate the fog, or electrical discharges to 
make it fall, have been tried. Some of them have succeeded in clearing the air 
for spaces of 50 to 200 yards in front of the apparatus. 

In some places where fogs are frequent and heavy, they are an important 
source of moisture. The distribution of the redwood tree in California corresponds 
closely to the zone over which fogs extend inland. Along some African rivers the 
moisture from valley fogs, always drifted one way by the winds, causes heavier 
vegetation on one bank than on the other. Attempts by men to utilize the moisture 
of fogs have never proved very successful. 

Clouds and fogs affect temperature by hindering radiation. A 
cloudy night is not generally so cold as a clear one. Cloud and fog 
during the day-time hinder the usual daily rise of temperature, by 
shutting out the sun's heat. In general, cloudiness lowers the sum- 
mer temperature of middle latitudes, and raises the winter tempera- 
ture. Heavy fogs have had an influence in war. Thus a fog helped 
Washington in his retreat to New York, after the battle of Long 
Island. 

Forms of clouds. Clouds take many forms. Among the more 
common are the cumulus, the stratus, the nimbus, and the cirrus 
clouds. 

Cumulus clouds are thick, and their upper surfaces are somewhat 
dome-shaped, with irregular and fleecy projections. Their bases are 
nearly horizontal (Fig. 46). They are formed from the water vapor 



9 6 



ELEMENTS OF GEOGRAPHY 



in ascending convection currents, and their level bottoms seem to 
mark the altitude at which condensation takes place as the air rises. 
Their bottoms are usually somewhere from i ,800 to 4,000 feet above 
the land, but the tops may rise three or four miles higher. • They 
appear, especially in clear, hot weather, in mid- or late-forenoon, after 




Fig. 46. 



Fig. 47. 





Fig. 46. 
Navy.) 

Fig. 47- 
of Navy.) 

Fig. 48. Cirrus clouds 



Fig. 48. Fig. 49. 

Cumulus clouds. (Cloud chart, Hydrographic Office, Dept. of 



Cumulo-nimbus clouds. (Cloud Chart, Hydrographic Office, Dept. 



Fig. 49- 
of Navy.) 



(Cloud Chart, Hydrographic Office, Dept. of Navy.) 
Cirro-stratus clouds. (Cloud Chart, Hydrographic Office, Dept. 



insolation has established convection currents. They attain their 
greatest size at about the hour of maximum heat. As evening ap- 
proaches they commonly grow smaller. 

Stratus clouds are horizontal sheets of cloud, often not more than 
1 ,000 feet above the earth. 



CLIMATIC FACTORS: MOISTURE 97 

Nimbus or rain clouds (Fig. 47) consist of thick masses of dark 
clouds without definite shape and with ragged edges, from which 
continued rain or snow generally falls. Nimbus clouds are rarely 
more than half a mile above the earth's surface. ■ 

Cirrus clouds are delicate, fibrous, or feathery (Fig. 48). They 
are generally white, and sometimes arranged in belts. They are 
usually high, five miles or more, and thin, and probably always 
consist of particles of snow or ice. 

Between these types of clouds there are many gradations of which 
perhaps the most interesting is the cirro-stratus (Fig. 49), a thin, 
veil-like cloud, almost imperceptible, usually extending in a sheet 
over a large part of the sky. 

When rays of light from the sun or moon pass through the ice particles of 
which the cloud is made, the rays are turned aside {refracted), and cause a ring, or 
halo, around the sun or moon. Popular belief in many places makes the halo a 
sign of coming storm, a belief which has some foundation in fact, because cirro- 
stratus clouds usually are associated with general storm areas. 

In general, cirrus and cumulus clouds are fair-weather clouds, 
and do not give precipitation. The latter, however, may grow into 
the cumulo-nimbus or summer thunder cloud, losing its fleecy white- 
ness, and produce rain. Cirro-stratus, stratus, and nimbus clouds 
are more likely to be foul-weather clouds. 

Cloudiness and sunshine. The chief importance of clouds is 
found in their relation to (1) precipitation; and (2) sunshine. Clouds 
cut off sunshine (Fig. 50) and reduce the amount of insolation; hence 
they lower day-time temperatures. Clouds also check radiation, and 
so tend to keep night temperatures higher, which means less likelihood 
of frost when the temperature is near the freezing point. Cloudy 
localities, therefore, have less variable temperatures than clear ones. 
Through their effect on temperatures, clouds also affect humidity 
and evaporation, raising humidity and lowering evaporation. Hence 
cloudy localities are generally cool and damp; as a result, the types 
of vegetation and the crops grown there are different from those of 
places in the same latitude where clouds are few. Thus vineyards 
are rarely found in cloudy regions, wine production being typical of 
sunny countries. 

In general, great cloudiness goes with great relative humidity 
(Figs. 44 and 50). Thus cloudiness is somewhat greater in winter 
than in summer, greater in higher latitudes than in low ones, and 



9 8 



ELEMENTS OF GEOGRAPHY 




Fig. 50. Map showing mean annual number of hours of sunshine in the 
United States. (After Van Bebber.) 

greater along sea-coasts than in continental interiors. The sunniest 
parts of the earth are hot deserts. 

The matter of hours of sunshine is also important in connection with the using 
of the direct heat of the sun as a source of power. In many dry countries, where 
fuel is scarce, it is customary, when hot water is needed, to expose it to the direct 
rays of the sun in a black vessel. The temperature of water may be raised, in this 
way, as high as 140 F., after which less fuel is necessary to boil it. Acting on this 
principle, various devices have been invented to gather the heat from a large area 
and concentrate it for the purpose of generating steam for an engine. From the 
actual operation of solar engines it appears that the amount of heat from 100 
square feet of surface will give one horse power for 8 or 9 hours a day. Calculated 
on this basis, a small part of the sunny section of Arizona would yield many times 
as much power as is used in the entire country at present. This source of power 
may be a great asset in the distant future. 

Precipitation. The condensation of the water vapor of the air 
leads to rain, snow, or hail, if the products of condensation fall. 
Whether precipitation really takes place after the formation of clouds, 
depends on many conditions. To give rain or snow, the particles of 
water or snow in the cloud must be large enough to fall. Drops of 
rain vary in diameter from V50 to J /s of an inch. If they are to reach 
the ground they must not pass through air which is dry enough and 
warm enough to evaporate them before they reach the bottom of the 



CLIMATIC FACTORS: MOISTURE 99 

atmosphere. In desert regions, water may sometimes be seen to be 
falling from a high cloud, when not a drop reaches the ground. The 
falling drops evaporate as they descend. 

Precipitation and evaporation. The distribution of rainfall 
depends, in large measure, on the winds, and will be considered later. 
The amount and distribution of precipitation, as they concern plant 
life, however, are connected intimately with the amount of evapora- 
tion. Thus two localities which have the same rainfall may have 
very different sorts of plants, because more of the precipitation in 
one place returns quickly to the atmosphere through evaporation. 

In some parts of western Texas, with a precipitation of 22 inches, there is 
moisture enough for various kinds of hardy grasses and for "dry-farming" (p. 498), 
yet the region is given over largely to grazing. In the valley of the Red River in 
Minnesota and North Dakota the precipitation is a little less; yet this is one of the 
most important wheat regions of the world. The difference between the two regions 
is due chiefly to the fact that evaporation is about 2]A. times as great in Texas as 
in the Red River Valley, because of the higher temperature in the former place. 

In many other localities where rainfall is scanty, evaporation is one of the 
most important of all climatic factors, so far as vegetation is concerned. Dry- 
farming depends partly on the principle that if evaporation from the soil is 
checked, even scanty rainfall (15 inches yearly) may suffice for hardy crops like 
wheat. In many parts of the West, also, rows of trees are planted or high fences 
built to act as wind breaks, and to check evaporation from gardens. The so-called 
"hot winds" which sometimes do great damage to the corn crop, as in Kansas and 
Nebraska, owe their destructiveness chiefly to the rapid evaporation caused by 
their high temperature and extreme dryness. If these winds were moist, their 
temperature would not hurt the corn. Desert plants have peculiar characteristics, 
as fleshy leaves and smooth, shining surfaces, developed apparently with 
reference to preventing loss of moisture by evaporation. 

Artificial Condensation 

From a desire to increase the rainfall of arid regions, or relieve 
droughts in other sections, various attempts have been made to pro- 
duce rainfall. The methods tried have been various, but the results 
have all been failures. The plan most tried has been that of pro- 
ducing explosions of some sort in the air well above the land. One 
reason for trying this method was found in the popular belief that 
great battles, with much cannonading, are followed by rain. So far as 
the belief in rain after battles is well founded, it is probably to be 
explained in some other way. Man has not yet succeeded in pro- 
ducing rain on any important scale, and is not likely to. If there 
were many cloud particles in the air, the jar of an explosion might 



ioo ELEMENTS OF GEOGRAPHY 

perhaps cause them to unite, and so make them large enough to fall; 
but the amount of rainfall which can be thus produced, under the 
most favorable conditions, is probably too small to be of consequence. 
The other methods which have been tried or suggested seem equall) 
useless. 

Questions 

i . What are the results of the fact that evaporation is faster at Denver than 
at Milwaukee? 

2. Why is the crop in a grain field poor around the base of a tree? 

3. Why does wind increase the rate of evaporation? 

4. Where, in middle latitudes, would you expect the sensible temperature to 
be highest in summer? In winter? The same for tropical regions. 

5. What is the effect on sensible temperatures of the relative humidity which 
prevails in houses in winter? 

6. Why is the humidity in houses in winter different from that out of doors, 
even where the furnace has a supply pipe taking in outside air? 

7. What is the effect of the indoor winter humidity on the amount of fuel 
burned? 

8. Beds of rock salt are found underground in some places. What con 
elusion may be drawn as to the climate when the deposit was formed? 

9. Why does fog in the evening appear first close to the ground? 

10. Why are clouds rarely formed above an altitude of 10 miles? 

11. Why does most of the heavy precipitation come from low clouds? 

12. In what parts of middle latitudes might the sun's heat be regarded as a 
possible source of power? In what parts not? Why? 

13. What is the reason for the formation of more dew on surfaces of stone or 
metal than on pieces of wood near by? 

14. Explain the fact that the lower leaves or branches of a plant may be 
nipped by frost, when the upper parts of the same plant are unaffected. 

15. Why are frosts less common after heavy rain than at other times? 

16. Why does a covering of newspapers or of thin cloth often protect plants 
from frost? 

17. Suggest other means by which protection from frost might be secured for 
large fruit orchards and truck farms. 

18. In what ways may plants in a house be beneficial to the air? 
19.' At what time of day is humidity lowest, on the average? Why? 

20. Why does high humidity in summer tend to make the air feel warmer 
and in winter make it feel colder? 

21. Explain the distribution of sunshine as shown in Fig. 50. 



CLIMATIC FACTORS: MOISTURE 101 



References 

Clayden: Cloud Studies. (London, 1905.) 

Davis: Elementary Meteorology, Chs. VIII, IX. (Boston, 1894.) 

Failyer: Management of Soils to Conserve Moisture; Farmers' Bull. No. 266, 

U. S. Dept. Agri. 

Gannett: The Relation of Rainfall and Temperature to Tree Growth, in Bull. 

Am. Geog. Soc, Vol. XXXVIII, pp. 424-434. 

Hann: Handbook of Climatology, Chs. II, VIII, XVI. (New York, 1903.) 
Moore, W. L.: Descriptive Meteorology, Chs. XI, XII. (New York, 1910.) 
Russell, W. J. : Town Fogs and Their Effects, in Nature, Vol. XLV, pp. 10-16. 
Ward: Relative Humidity of Our Houses in Winter, in Jour. Geog., Vol. I, 

pp. 310-316. 

Ward: Sensible Temperatures, in Bull. Am. Geog. Soc, Vol. XXXVI, pp. 

129-137. 



CHAPTER VII 
CLIMATIC FACTORS: PRESSURE AND WIND 

Pressure 

Importance of pressure. The downward pressure (or weight) 
of the air is about 15 pounds to the square inch at sea-level. The! 
pressure varies a little from time to time at any given place, and is 
rarely the same at any two places more than a 
few miles apart. In themselves, variations of 
pressure have little effect on life; but the varia- 
tions have much to do with winds and other 
elements of weather, and weather is most impor- 
tant to life. Hence it is desirable to have some 
simple method of measuring and recording at- 
mospheric pressures. The instrument by which 
the pressure of the atmosphere is measured is 
the barometer. 

The barometer. The principle of the barom- 
eter is as follows: A tube more than 30 inches 
long, closed at one end, is filled with mercury. 
The open end of the tube is then placed in a dish 
of mercury (Fig. 51). The mercury in the tube 
will sink until its upper surface reaches a level 
about 30 inches above the level of the mercury in 
the dish, if the place of the experiment is at sea- 
level. The mercury remains at this level in the 
tube, because the pressure of the air on the mer- 
cury in the dish is enough to balance the weight 
of the mercury in the tube. Since the pressure 
of the air at sea-level balances a column of mer- 
cury about 30 inches high, the pressure of the 
air at sea-level is said to be 30 inches (or 760 
millimeters). If the pressure is more than 30 inches it is said to be 
high; if less than 30 inches, it is said to be low. At sea-level the 



Fig. 51. Diagram 
to illustrate the prin- 
ciple of the barom- 
eter. The pressure 
of the air at A main- 
tains the mercury at 
B in the tube when 
there is no air in the 
tube above B. 



CLIMATIC FACTORS: PRESSURE AND WIND 103 

variation above and below 30 inches is rarely more than one inch. 
Changes of pressure with changing altitudes are much greater. 

Pressure and altitude. At elevations above sea-level the pres- 
sure grows less, as shown in the following table: 

Altitude Above Normal Barometric 

Sea-Level, in Feet Pressure, in Inches 

o, as at New York 30 

1,800, as at Spokane, Washington 28 

3,800, as at El Paso, Texas 26 

5,900, as at Colorado Springs, Colorado 24 

8,200, as at Bogota, Colombia 22 

10,600, as at Leadville, Colorado 20 

16,000, as at St. Vincente, Bolivia 17 



At an altitude of six miles, a little above the highest point of land, 
the pressure is less than one-fourth the normal for sea-level. 

The rate of decrease of pressure with increasing height being known, 
the altitude of a place above sea-level may be measured by means 
of the barometer. A special 
form of barometer, the aneroid 
barometer (Fig. 52), has been 
devised for this purpose. 

The pressure at 10,600 feet, 
approximately two miles, is about 
10 pounds to the square inch. 
As a result, water passes more 
readily into steam when heated; 
hence its boiling temperature is 
lower with decreased pressure. 
Pressure and boiling tempera- 
ture bear a nearly constant ra- 
tio to each other — the boiling 
point being lowered about i° F. 
for each 550 feet of altitude, or 
for every 0.589 inch of baromet- 
ric fall. This principle may, 
therefore, be used to determine 
heights above sea-level. Thus 
on top of Pike's Peak, water boils at about 186 F. or 26 below the 
boiling temperature at sea-level (212 ); its altitude therefore is a 
little over 14,000 feet. 




Fig. 52. Aneroid barometer. The 
needle moves to the right as the atmos- 
pheric pressure increases, and to the left 
as it decreases. 



io4 ELEMENTS OF GEOGRAPHY 






Such a condition makes cooking by boiling very difficult or impossible at 
high altitudes. Thus for Leadville, more than 10,000 feet above sea-level, many 
of the cooking recipes of Chicago or New York would be unsuccessful unless 
allowance were made for the lower boiling point. The decrease of pressure explains 
some of the discomforts, such as mountain sickness, experienced by many mountain 
climbers. Bleeding from the nose, nausea, and headache, the most common effects, 
are due to the fact that the blood pressure in the body is adjusted to the atmospheric 
pressure at lower altitudes, and does not readjust itself quickly enough to the 
changing conditions as one ascends, especially if the ascent is rapid. After a short 
stay at relatively high altitudes, these discomforts disappear in most cases. An 
analogous effect is produced on workers in high-pressure air-chambers (caissons), 
such as are used in laying foundations for bridge piers. Not infrequently the men 
work under an air pressure three or four times the normal at sea-level. Coming 
too quickly from the caissons into the open air, men are in some cases stricken with 
the dread caisson disease, which usually proves fatal in a few hours. Deaths 
as the result of unwise ascents to high altitudes are not unknown, but in most 
cases they are due not so much to lower pressure, as to weakness of the heart, and 
its need for greater activity on account of diminished supply of oxygen. 

Distribution of pressure. The pressure of the atmosphere at 
sea-level varies from point to point, and from time to time at the 
same point. Some of the reasons are as follows : 

(1) The temperature of the surface on which the air rests is 
unequal, and increase of temperature makes the air lighter. As the 
temperature varies, the pressure varies. 

(2) Water vapor in the air makes the air lighter because it dis- 
places some of the oxygen, nitrogen, and other constituents which 
weigh more than the vapor. The amount of moisture in the air is 
greater in warm regions (but not in hot deserts) than in cold ones, 
and greater over moist surfaces than over dry ones. Since the amount 
of moisture in the air varies from time to time, the pressure is con- 
stantly changing. 



Representation of Pressure on Maps and Charts 

Isobars. For convenience in the study of pressure distribution, 
lines may be drawn on maps connecting points where the atmospheric 
pressure is the same, analogous to the lines connecting points having 
the same temperatures. Such equal-pressure lines are isobars. A 
map showing lines of equal pressure is known as an isobaric map or 
chart. An isobaric chart for the year shows isobars connecting points 
having the same average pressure throughout the year. There may 
be isobaric charts for a season, for a month, or for shorter periods 
The daily weather maps are daily isobaric charts. Fig. 53 represents 



. 



CLIMATIC FACTORS: PRESSURE AND WIND 105 




bo 



io6 ELEMENTS OF GEOGRAPHY 









an isobaric chart for the year. The figures on the lines indicate the 
average pressure for the year in inches. 

In the southern hemisphere, the isobar of 30 inches encloses a 
belt extending almost around the earth, being interrupted only in 
the vicinity of Australia. Every point within the area enclosed 
by this isobar has an average atmospheric pressure of more than 30 
inches. Every point within the isobar of 30.10 inches has an average 
annual pressure of more than 30.10 inches, while every point between 
the isobars of 30 and 30.10 has an average annual pressure of more 
than 30 and less than 30.10 inches, etc. Between the two adjacent 
isobars of 29.90 in the equatorial part of the Atlantic, the pressure is, 
on the average, less than 29.90, but not so low as 29.80. If the 
pressure sank to the latter figure, there would have been isobars 
of 29.80 inches. 

It will be remembered that in the case of the temperatures shown 
on an isothermal chart allowance is made for altitude above sea-level. 
In the same way, the pressures shown on land on an isobaric chart 
are those which would exist if there were no elevations above sea- 
level. The allowance for altitude is not a constant figure, but varies 
with the temperature and the pressure. For low altitudes the 
pressure decreases about .1 inch for each 90 feet of rise. 

Relation of isobaric surfaces and air movement. An isobaric 
surface connects places having the same air pressure. If, for example, 
one place at sea-level has a pressure of 30 inches, and another a pres- 
sure of 30.10 inches, the isobaric surface of 30 inches is above sea- 
level at the place where the pressure is 30.10 at sea-level. If the 
pressure at sea-level at another place is 29.90 inches, the isobaric 
surface of 30 inches is below sea-level there. An isobaric surface, 
therefore, may have slopes. 

Fig. 54 shows a series of isobars, with the pressure least at the 
center, and Fig. 55 shows the slope of the isobaric surfaces in 
the same area. Fig. 56 shows another series of isobaric lines, with 
the pressure greatest at the center, and Fig. 57 shows the slope of 
the isobaric surfaces in the same region. 

If a surface of water had the form shown by the uppermost line 
in Fig. 55, the water would flow in from all sides until the surface 
became level. If the water surface had the form shown in Fig. 57, 
the water would flow away from the top in all directions. The air, 
which is more fluid than water, acts in a similar way, and moves down 
the slope of any isobaric surface. Such movements of air are winds 



CLIMATIC FACTORS: PRESSURE AND WIND 107 



From these figures it 
may be seen that wind 
blows toward areas of 
low pressure, and from 
areas of high pressure. 
When the isobaric slope 
(or isobaric gradient) is 
high, the wind is strong; 
when the isobaric gra- 
dient is low, the wind is 
gentle; and when there 
is no isobaric gradient, 
that is, when the iso- 
baric surface is level, 
there is no wind. The 
strong wind is strong 
for much the same rea- 
son that a swift river is 
swift; the gentle wind 
is gentle for much the 
same reason that the 
slow river is sluggish; 
while the absence of 
wind may be compared 
to the pond in which 
there is no perceptible 
current, because there is 
no slope of the surface. 
Courses of isobars. 
Returning now to Fig. 
.53, several points are 
readily seen: (1) The. 
isobars have a general 
east-west course, 
though many of them 
are not straight; (2) on 
the average, they show 
greater pressure in low 
latitudes than in high 
latitudes; (3) they are 




Fig. 54. A series of isobaric lines showing 
decreasing pressure toward the center. 

Fig. 55. Section through Fig. 54, showing the 
slope of isobaric surfaces. It will be seen that 
isobaric lines are the lines where isobaric surfaces 
cut sea-level. 

Fig. 56. A series of isobaric lines showing 
increasing pressure toward the center. 

Fig. 57. Section through Fig. 56, showing the 
slope of isobaric surfaces. 



io8 



ELEMENTS OF GEOGRAPHY 




CLIMATIC FACTORS: PRESSURE AND WIND 109 

highest (that is, they show highest pressures) in the latitudes just out- 
side the tropics ; (4) they are more regular in the southern hemisphere 
than in the northern; and (5) they are, on the whole, more regular 
on the sea than on the land. 

The isobaric map for January (Fig. 58) shows also that a high- 
pressure belt is very wide in the northern hemisphere, especially on 
the land, which at this season (winter) is cooler than the sea. This 
fact suggests that high pressure goes with low temperature. In the 
southern hemisphere, January is a summer month, and the land is 
warmer than the sea. If high temperature causes low pressure, the 
pressure in the southern hemisphere at this time should be less than 
that in the northern, and it should be lower on the land than on the 
sea. The map shows that both these things are true. This chart, 
therefore, seems to show that high temperature reduces pressure. 

A study of the isobaric chart for July (Fig. 59) leads to the same 
conclusion. At that time of year, the pressure in the southern hemi- 
sphere (winter) should be higher, on the average, than in January 
(Fig. 58) ; especially should it be higher on land, as the map shows it 
to be. In the northern hemisphere in July, on the other hand, the 
pressure should be less than it was in January, and especially should 
it be less on land, which is much warmer than it was in winter. Fig. 
59 shows both these things to be true. We have confidence, there- 
fore, in the conclusion that high temperature reduces the pressure, 
while low temperature increases it. The charts furnish other evi- 
dences in support of the same conclusions. 

If temperature alone controlled pressures, they should be lowest 
near the equator, where it is warmest, and highest near the poles, where 
it is coldest. Fig. 53 shows that the average annual pressures are 
distributed in apparent disregard of temperature, for the pressures 
are highest neither where it is coldest nor where it is warmest. It 
is clear, therefore, that neither temperature nor latitude entirely 
controls the distribution of pressure. 

Isobars and humidity. We have seen (p. 104) that water, 
vapor makes the air lighter. But the isobars are not lowest over the 
oceans in warm latitudes, where the air contains, on the average, most 
moisture. We conclude, therefore, that the amount of moisture in 
the air is not the chief factor controlling the isobars. 

Inequalities of temperature and moisture in the air are the only 
factors thus far studied which might affect the isobars; and since 
they do not explain the most striking feature in the distribution of 



no 



ELEMENTS OF GEOGRAPHY 




CLIMATIC FACTORS: PRESSURE AND WIND in 

atmospheric pressure, namely, the high pressures in relatively low 
latitudes, we conclude that something besides temperature and mois- 
ture must be involved in their explanation. 

The high-pressure belts. The explanation of the high pressure 
in low latitudes, rather than in high, and the explanation of the 
highest pressures just outside the tropics, are not found on the isobaric 
charts. These larger features of pressure-distribution are to be 
explained by the general circulation of the atmosphere under the 
influence of rotation (p. 112). 

Winds 

Importance. Horizontal movements of the air are winds. 
Winds are important in many ways, as in carrying away the impuri- 
ties of city air, in spreading dust and sand (p. 313), in erosion 
(p. 314), in furnishing power for windmills and sailing vessels, 
in increasing evaporation (p. 88), and in distributing the moisture 
of the air. Winds also affect human beings directly, for they lower 
the sensible temperature, and are, as a rule, stimulating and invigor- 
ating, while calm air (if warm) is enervating. In all these ways the 
fact of air movement is important. 

Winds are produced by inequalities of pressure at the same 
level. These inequalities are being renewed constantly by unequal 
heating, and in other ways; hence winds are always blowing, and 
there is a general circulation of the atmosphere from regions of 
greater pressure to those of less pressure at the same level. 

Relation of winds to the distribution of insolation. If the 
air over the whole earth were quiet at a uniform low temperature, 
and if it could then be heated by the sun for a time without any 



90° 0° 90° 

Fig. 60. The lower line may be taken to represent the surface of the earth; 
the upper solid line, the outer surface of the atmosphere as it would be if the 
temperature were everywhere equal. The dotted line shows the effect of heating 
on the surface of the air. Movement would result as indicated by the arrows. 

horizontal movement, the effect would be to raise its surface every- 
where, and to raise it most where it was heated most, that is, in low 
latitudes (Fig. 60). Under these conditions there would be a baro- 
metric slope from low latitudes toward high latitudes. Before 



ii2 ELEMENTS OF GEOGRAPHY 

horizontal movement began, there would be no change of pressure 
at the bottom of the air, for the same amount (mass) of air would 
lie over each place, as before the heating. But if the surface of 
the air had the form shown by the dotted line in Fig. 60, the upper 
air would move as shown by the arrows. Since the air in low lati- 
tudes is always warmer than that in high latitudes, the upper air 
should always be moving from the equatorial zone toward the polar 
zones in both hemispheres. These poleward movements of the 
upper air lessen the pressure at the bottom of the atmosphere in 
low latitudes, because air has moved away from them. After 
air has moved from the equatorial region toward the poles (Fig. 60), 
there is more air over a given spot in high latitudes than in low. A 
barometric gradient is thus established toward the equator at the 
bottom of the atmosphere. Air then moves from higher latitudes to 
lower latitudes at the bottom of the air (Fig. 61). 






90° 0° 90° 

Fig. 61. The movement of air indicated in Fig. 60 would result in further 
movement as shown by the lower arrows in this figure. 

Here, then, we have the elements of a general circulation, a 
poleward movement in the upper air, and an equatorward movement 
in the lower air, and the unequal heating which generates these move- 
ments is in operation all the time. 

If the earth did not rotate, these movements of air would tend 
to follow meridians. The poleward-moving air would blow north 
in the northern hemisphere, and south in the southern, while the air 
moving toward the equator would blow south in the northern hemi- 
sphere, and north in the southern. Rotation, however, turns the air 
currents to the right in the northern hemisphere, and to the left in the 
southern. 

Effect of the extra-tropical belts of high pressure. Let us 
now note the effect of the high-pressure belts just outside the tropics 
(Fig. 53) on the circulation of the air. From these belts the air flows 
to areas of lower pressure on either side, at the bottom of the 
atmosphere, giving rise to distinct wind zones. 

Wind zones. The winds blowing poleward from the high- 
pressure belts are turned toward the east in both hemispheres, and 



CLIMATIC FACTORS: PRESSURE AND WIND 113 



so become westerly winds (southwesterly in the northern hemisphere, 
and northwesterly in the southern). The winds blowing from the 
belts of high pressure toward the equator become easterly winds (north- 
easterly in the northern hemisphere, and southeasterly in the south- 
ern), and are known as trade-winds (Fig. 62). Sailing west from 
the Canary Islands to find Asia, 
Columbus came under the influ- 
ence of the trade-winds, which 
bore him steadily across the 
Atlantic. Thereafter, many sea- 
men from Europe followed this 
course. The zone along the 
thermal equator, where the 
northeasterly and southeasterly 
trades meet, and where rising 
currents of air are stronger 
than horizontal movements, is 
known as the zone of equatorial 
calms, or "doldrums" a region 
dreaded by the crews of sailing 
vessels, as much as the trade- 
winds were welcomed. The 




Fig. 62. Generalized diagram of 
wind directions at the bottom of the 
atmosphere. 



position of this zone of calms shifts a little with the sun, its center 
remaining near the thermal equator (Fig. 95). 

The westerly winds of middle latitudes and the trades of low 
latitudes are the prevailing winds {planetary winds) at the bottom 
of the atmosphere. 

Periodic Winds 

When air is heated it expands, and a given volume of it becomes 
lighter. This results in movements of convection (Fig. 61). One 
of the movements involved in convection is horizontal, and horizontal 
movement of the air is wind. On a cold day in winter, with a brisk 
open fire, cold air may be felt moving along the floor toward the fire. 
Such movement is analogous to wind. Unequal heating of the air is, 
therefore, a cause of air movements, and since the air is being unequally 
heated all the time, unequal heating is a cause of constant atmospheric 
movements. Some of the movements are horizontal, and some 
vertical; some are in the lower part of the air, and some in the 
upper. 

The unequal heating of the air is the immediate cause of 



ii4 ELEMENTS OF GEOGRAPHY 

certain familiar winds and breezes, which blow at more or less 
regular periods and also interfere with the circulation indicated 
in Fig. 62. 

Land- and sea-breezes. On a sunny summer day, the land 
becomes warmer than an adjacent lake or sea (p. 63). The result is 
that the air over the land is warmed and expanded more than that 
over the sea. Movement of the air follows. By day, especially after 
some hours of heating, the air moves in from the water to the land, 
at the bottom of the atmosphere. This is the sea-breeze or lake-breeze. 
At night the land cools more than the water, and the movements 
of air are reversed, giving the land-breeze, which blows from the land 
to the water, at the bottom of the atmosphere. The sea-breeze is 
strongest during the summer in warm regions. In many places it is 
felt inland 20 to 30 miles. It lowers the temperature over the land 
to which it blows, and makes the conditions of life on many 
tropical coasts much more agreeable than they would be otherwise. 
It is partly because of the cool, refreshing sea-breeze that many people 
go to the sea-shore during the hot months. When the sea, or lake, 
breeze has the same direction as the prevailing wind, it is so strong 
occasionally (as at Valparaiso, Chile) that business is stopped, and 
people forced to seek shelter. Along certain coasts, fishermen put 
to sea in the early morning with the land-breeze, and return toward 
night with the sea-breeze. The land-breeze may be very faint at 
night in spite of a brisk sea-breeze by day, because the land may not 
reach a temperature more than a few degrees below that of the water. 
The inequality of temperature is then not great enough to cause a 
distinct land-breeze. Fishermen and others who have, stayed out 
after the sea-breeze stopped have been becalmed, 'and in some cases 
compelled to stay out all night. 

The daily land- and sea-breezes are not usually felt far from shore, 
and do not extend to great heights. Breezes corresponding to land- 
and sea-breezes are often felt about large lakes. The sea-breeze is 
of consequence, not only by lowering the temperature of the land 
in hot weather, but by bringing pure air to the land. This is of much 
importance in influencing the development of shore resorts, and in 
making habitable many sections of tropical coasts. The effect of 
the daily sea-breeze on a tropical coast may be seen from the accom- 
panying table of temperatures recorded at a station on the west 
coast of Africa, at different hours before (up to 12:30) and after 
(after 12:30) the breeze sprang up. 



12 


I 2 130 P. 1 


1. 12:45 


1 


3 


N-E 


N-E 


N-W 


N-W 


N-W 


IOO° 


I02° 


82° 


78 


75° 


4% 


3% 


45% 


61% 


65% 



CLIMATIC FACTORS: PRESSURE AND WIND 115 

Hour 6 a. m. 8 10 

Wind Direction... E-N-E E-N-E N-E 

Temperature 70 8i° oi° 

Relative Humidity. 43% 24% 14% 

The effects of the sea-breeze are so beneficial in many places in 
the tropics that the natives of those regions call the sea-breeze the 
"doctor." 

Monsoons. Some lands near the sea become so much heated in 
summer that the sea (from-sea) winds continue during the hot sea- 
son, not merely through the hot part of the day, while the land 
(from-land) winds hold sway during the winter. This is the case, 
for example, in India. Such winds, which change their directions 
with the seasons, are monsoon winds. 

India is in the latitude of the northern trades, where north- 
easterly winds should prevail, if the planetary system (Fig. 62) were 




Fig. 63. Fig. 64. 

Fig. 63. The isobars of India for January. (Bartholomew.) 
Fig. 64. The wind directions of India in winter. (Koppen.) 



not interfered with. In Fig. 63 the gradient is from north to south, 
and the direction of the wind (Fig. 64) is in harmony with the planet- 
ary system (Fig. 62); but in Fig. 65 the isobaric gradient is to the 
northward, because the land is warmer than the sea, and the winds 
in the lower part of the air blow as shown in Fig. 66. That is, the 
planetary (northeast) wind is overcome during the hot season by the 
winds which result from the seasonal change of temperature. At 
the same season, the low pressure north of India, developed by the 
heat of summer, replaces the high pressure common in this latitude, 
and the prevailing trade-wind is displaced by seasonal winds. Figs. 



n6 



ELEMENTS OF GEOGRAPHY 



67 and 68 show the isotherms for the same region at the corresponding 
seasons, and make clear the relation between pressure and tem- 
perature. 




Fig. 65. Fig. 66. 

Fig. 65. The isobars of India for August. (Bartholomew.) 
Fig. 66. The wind directions of India in summer. (Koppen.) 

Monsoon winds influenced greatly the development and conduct 
of trade on the Indian Ocean. The systematic use of these winds 
caused a great expansion of the early trade between the Red Sea 




Fig. 67. Fig. 68. 

Fig. 67. Isotherms of India for January. (Buchan.) 
Fig. 68. Isotherms of India for August. (Buchan.) 

region and the East, and helped make Alexandria the commercial 
metropolis of the Roman Empire. Trading fleets left Berenice 
(western shore of the Red Sea) in July, when the southwest monsoon 



CLIMATIC FACTORS: PRESSURE AND WIND 117 

would carry them to India, and started back about the first of January, 
so as to take advantage of the northeast winter monsoon. Later, 
vessels sailing from Europe timed their outward and homeward voy- 
ages so as to take similar advantage of these winds. Indeed until 
the time of steamships, all commerce on the Indian Ocean continued 
to be connected closely with the monsoons. Important early political 
expansions also followed in the track of the same winds. The mon- 
soon winds of India have much to do with bringing moisture from 
the ocean, thus influencing the rainfall upon which the crops to feed 
250,000,000 people depend. 

Monsoon winds are not confined to India, though this name is 
not applied to all winds of this sort. In their summer seasons, 
all land areas are warmer than adjoining bodies of water; hence at 
any given altitude the pressure will decrease toward the land inte- 
rior. This means an isobaric slope toward the land, as a result 
of which there will be a tendency for air to flow landward from the 
sea. In winter the reverse is the case, and the air movement will 
be from the land area toward the sea. If the air movement is with 
the prevailing wind, the latter is strengthened; if it is against the 
prevailing wind, it weakens the latter, or overcomes it altogether. 
Such continental and oceanic winds are developed well on the east 
coast of Asia. Spain, in the zone of westerly winds, affords another 
excellent example of seasonal winds. Winds due to the same cause 
are felt about the Great Lakes. 

Mountain- and valley-breezes. Winds due to changes of tem- 
perature sometimes blow about mountains. Mountain-breezes blow 
from the mountains at night, and valley-breezes blow toward them 
on sunny days. Hence localities which are hot by day may be so 
situated as to receive cool mountain-breezes at night, making 
the nights comfortable. Various summer resorts benefit from such 
conditions. 

Besides the planetary winds, the seasonal winds (monsoons), 
and minor periodic winds (such as land- and sea-breezes) whose times 
of blowing are more or less regular, there are numerous winds which 
blow at irregular times, and whose coming cannot be foretold long 
in advance. These irregular "winds are the chief cause of the 
uncertain elements of the weather. Some of them are due to unequal 
temperatures, some to unequal amounts of atmospheric moisture, 
and some to other causes. These irregular winds will be considered 
in the next chapter. 



n8 ELEMENTS OF GEOGRAPHY 

Velocity and direction of the wind. Wind direction is shown 
by a weather vane, which points toward the quarter from which the 
wind is blowing. Wind directions are shown on maps by means of 
arrows which point toward the quarter to which the wind is blowing. 
Wind velocities are measured by an anemometer — - constructed on 
the same principle as the cyclometer on a bicycle — which shows 
the number of miles travelled in any interval of time. Wind veloci- 
ties, however, are expressed usually in miles per hour; thus trade- -\ 
winds are said to blow from 10 to 30 miles an hour. The United 
States Weather Bureau also uses descriptive terms (as light, fresh, 
brisk) for a regular scale of wind velocities. 

A wind velocity of 60 miles per hour causes a wind pressure of I 
nearly 10 pounds per square foot at sea-level, while at 90 miles an i J 
hour this pressure is doubled. Hence the destructive violence of 
winds of high velocity. 

In general, the average velocity of winds is greatest in latitude 
50 or thereabouts. The average velocity for the United States has 
been estimated at about 9.5 miles per hour, and for Europe 10.3. The 
velocity of winds is, in general, greater over the sea than over the land, 
largely because moving air is checked on land by friction with the 
uneven surface. It is greater in the upper air than in the lower, for the 
same reason. But the force of the wind at high altitudes is less than 
for the same velocities at sea-level, owing to the lesser density above. 
The average velocity is greater in winter than in summer, because the 
barometric gradient between the equator and the pole of the hemi- 
sphere having winter is greater than that of the other hemisphere. 

The greatest velocities, rising to 100 or more miles per hour, 
always are associated with irregular winds, and it is to them that the 
most destructive wind action is due. Some irregular winds blow 
from directions very different from those of prevailing winds. In 
middle latitudes, the sudden changes of temperature always are due 
to winds of this class. 

Winds and Rainfall 

Importance of rainfall. Perhaps the most useful service of the 
wind is in the distribution of the moisture evaporated from ocean 
and land. Rainfall is of great importance to all plants and animals 
which live on the land. Few plants live in desert regions, and few 
animals live where plant life is scanty. Human industries, too, are 
much affected by rainfall, for no arid region supports a dense popula 



CLIMATIC FACTORS: PRESSURE AND WIND 119 

tion, and no agricultural country, aside from small irrigated areas, 
can be prosperous, if the rainfall is unreliable. 

Less than one-thirtieth of the people of the United States live in the third of 
the country where the rainfall is less than 20 inches per year. Soil is not productive 
unless adequately watered, even though it be rich in the elements necessary for 
plant food. Rainfall also plays a large part in determining the character of many 
soils. Thus in some dry regions, the sandiness of the soil is due to the lack of 
moisture, without which that sort of mineral decay necessary to form clay cannot 
take place. Some desert soils are alkaline, because the soluble compounds of 
sodium and potassium (known as alkalies) have not been removed by water. 
Most plants will not grow in alkaline soils. The absence of moisture retards the 
development of humus, an important part of good soils. 

Twenty inches of rain per year usually is considered to be the 
minimum for general agricultural purposes, but something depends 
on (1) temperature, (2) the soil, and very much on (3) the time of 
year when the rain falls, and (4) the rate of evaporation, as determined 
by temperature, soil, and wind. The warmer and drier the climate, 
the more the water needed for crops. The total amount necessary is 
less if it falls when the growing crops need it most. That the total 
amount of rain for a year may not be the most important thing may 
be shown by comparing two places with about the same annual 
amount, but differently distributed. For general agricultural pur- 
poses, without irrigation, Concordia is far ahead of Red Bluff. 

3.9 in. (6 months) 



Annual Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec. 

Red Bluff, Cal 25.7 4.7 3.5 3.2 2.1 1.3 0.5 0.0 0.0 0.6 1.5 3.0 5.3 

(Winter rain.) 20.2 in. (6 months) 



Concordia, Kas 26.8 0.7 0.8 1.5 2.3 4.7 4.3 3.7 2.9 2.4 2.2 0.8 0.5 

(Summer rain.) 

It is best for agriculture to have the rain come in the season when 
temperatures are most favorable for plant growth. Hence in middle 
latitudes, summer rain is of more value than winter rain. Rain or 
snow falling at times when plants are not growing is, however, not 
useless to them, for some of it remains underground, and is taken 
up by their roots at a later time. 

Irrigated land does not depend directly on rain and snow, but the 
water used in irrigation is derived from the atmosphere, though in 
many cases the water falls far from the place where it is used. Thus 
in the Indus Valley, millions of people are supported by irrigation 
from streams which get their water largely from melting snows in 



i2o ELEMENTS OF GEOGRAPHY 






the Himalaya Mountains. A very porous soil loses its moisture 
more quickly than a more compact one, and so needs more rain for 
crops. 

Rain and snow are important not only as a source of water for soil, but as a 
source of supply for streams and wells. A mantle of snow also prevents great 
changes in the temperature of the soil beneath, and in this way protects many 
plants. So important is this effect that in some regions a heavy snow generally 
means good yields of fall-sown crops the next year. Snow hampers some kinds 
of transportation and favors others. In lumbering, for example, snow makes 
the hauling of logs easier. Rapidly melting snow and heavy rainfall on frozen 
ground cause destructive floods. Heavy rain in a city is beneficial in flushing 
and cleaning the streets and in washing out of the air a large part of its impurities. 
On the other hand, it may flood cellars and basements, doing great damage. Rain 
and snow both hinder the circulation of dust and bacteria, thus further con- 
tributing to health. 



The distribution of rainfall is influenced largely by winds, which 
carry moisture from the places where it is evaporated to the places 
where it is precipitated (Fig. 69). Winds help to determine where 
rain falls, how much falls, and at what times of the year. The rate 
of rainfall also is important. More moisture may enter the soil from 
a light, gentle rain, than from a heavy downpour. Washing of the 
soil is also greater when torrential rains fall. We conclude that a 
given amount of water falling as light, gentle rains is better than a 
larger amount falling rapidly, for of the latter a large part runs off 
immediately (Why?). 

The precipitation of any given region depends largely on (1) what 
winds affect it, (2) the topography of the surface over which the 
winds blow before reaching it, and (3) the topographic situation and 
relations of the place itself. 

Relation of rainfall to general winds. In the trade-wind zones, 
the winds blow from higher to lower latitudes, and therefore, on the 
average, from cooler to warmer places. As the air is warmed, it 
can hold more moisture. So long as the trades blow over the sea or 
low land, they take moisture, but do not drop what they have. It 
follows that on the sea, and on comparatively low lands, like the 
Sahara, the trade-winds are "dry." A part of Australia lying in the 
belt of the southeast trades is also dry. 

If, however, the air of the trades is forced up over mountains, it 
is cooled, and some of its moisture may be condensed and precipitated. 
The windward sides of high mountains in the trade-wind zone have 
heavy rainfall. An illustration is afforded by the east side of the 









CLIMATIC FACTORS: PRESSURE AND WIND 121 




ELEMENTS OF GEOGRAPHY 






Andes Mountains in the trade- wind zone (Fig. 69). Another example 
is furnished by the volcanic cones of the Hawaiian Islands. The 
trade-winds yield little rain to their lower slopes, but, forced up over 
the mountains, they yield abundant moisture at higher levels. The 
levels of heavy rainfall may be readily seen, because of a change in 
the vegetation. Even in the middle of the Sahara and of Australia, 
some rainfall is caused by high hills and mountains which stand in 
the path of the trade-winds. 

After the air of the trades passes over a mountain range, it 
descends, and is warmed both by contact with the warm surface and 
by compression. It therefore takes up moisture. The leeward sides 
of mountains in the trade-wind zones are therefore regions of little pre- 
cipitation. The west slope of the Andes Mountains in the zone of 
the trades furnishes an example in the coastal desert of Peru. 

Rainfall in the zones of the prevailing westerlies. The prin- 
ciples which apply to the rainfall in the trade-wind zones apply also 
in the zones of the westerly winds. These winds are, on the whole, 
blowing from lower to higher latitudes, and so are being cooled grad- 
ually. They may, therefore, yield some moisture, even at sea-level 
or on low land, and especially on land in the winter season. The heat 
of the land in summer often prevents condensation and precipita- 
tion of the moisture in the westerly winds, until the air has moved 
far to poleward. But when such winds cross mountains, they yield 
moisture to their windward slopes and summits, and become dry on 
the leeward slopes (Fig. 69). 

From these principles we may understand the rainfall of the 
United States, so far as it depends on planetary winds. The pre- 
vailing winds, for most of the country, are from the southwest. 
Coming to the land from the Pacific Ocean, these winds find the 
land cooler than the ocean in winter, and warmer in summer. In 
winter they yield moisture, even at low levels. This gives the low 
lands of California their wet season. As the winds blow across the 
mountains back from the coast, they yield .more moisture, so that all 
the area west of the top of the first high ranges, the Sierras at the 
south and the Cascades at the north, is supplied with rain and snow 
in the winter season. As the winds blow beyond the Sierra Nevada 
and Cascade mountains, the air descends and becomes warmer, and 
therefore dry. East of these mountains lie the arid and semi-arid 
lands of the Great Basin with its Great Salt Lake, and of eastern 
Oregon and Washington. 






CLIMATIC FACTORS: PRESSURE AND WIND 123 

The effect of altitude on rainfall may be illustrated by the rainfall 
at different altitudes in crossing the Sierra Nevada range from the west. 

Altitude, Rainfall, 
feet inches 

Sacramento, W. side of range. 75 20 

Colfax, W. side of range 2,400 45 

Cisco, W. side of range 5,940 50 

Summit 7,000 46 

Carson City, Nev., E. side of range 4,674 10.8 

In general, precipitation increases up to an altitude of 4,000-6,000 
feet; above 6,000 feet it decreases generally. One important effect 
of increased precipitation at high altitudes is the great winter snowfall, 
amounting to 20 or 30 feet in some places. This interferes 
seriously with the business of railroads which cross such regions. 
The relation of precipitation to altitude is shown in the distribution 
of vegetation on mountains. Thus on the San Francisco Mountains, 
in Arizona, desert vegetation prevails up to an altitude of 5,900 feet, 
while from 6,800 up to 11,000 feet, various types of trees are found in 
abundance. 

When the westerly winds from the Pacific reach the higher parts 
of the Rocky Mountains, which are higher in many places than the 
mountains farther west, they again yield some moisture. But farther 
east, all the way to the Atlantic, these winds are dry, for they cross 
no more high mountains, and they do not generally go far enough north 
to reach a temperature as low as that of the mountains they have 
passed. For some distance east of the mountains the rainfall is slight; 
but east of central Kansas and Nebraska the lands are well supplied 
with moisture. It is therefore clear that something besides the 
westerly winds brings rainfall to this region. This agent is the 
irregular cyclonic wind, to be studied in the next chapter. 

The winds which blow from the Pacific to the continent in sum- 
mer have a different effect upon rainfall. At this time of year, they 
find a temperature on the coastal low lands higher than their own. 
They are therefore "dry" in this region, and give to much of Cali- 
fornia its dry season. Blowing inland, these winds reach mountains so 
high that the temperature is low enough to cause condensation and 
precipitation, even while the low lands to the west are dry. In 
Washington, the mountains near the coast are high enough to 
cause precipitation even in summer. In Alaska, where some 
of the mountains always are covered with snow, precipitation is 
heavy in summer, and at high altitudes much of it falls as snow. 



i2 4 ELEMENTS OF GEOGRAPHY 






Monsoon winds may yield much moisture. In general, they 
blow toward warmer regions, and so should be dry; but they may be 
forced up over high mountains, and precipitation follows. They are 
assisted also by convection currents over the warm land, in producing 
rainfall of the thunder shower type. The heaviest rainfall on record, 
on the southern slopes of the Himalayas, is due to monsoon winds. 
As in the case of the planetary winds, it is the windward sides of the 
mountains which receive the heavy precipitation from the monsoons. 
It is clear, therefore, that the windward sides of high mountains are 
places of heavy rainfall and snowfall. 

Land- and sea-breezes rarely yield much rain, though they may 
give rise to fogs when they blow from warmer water to cooler land, or 
when, at the opposite season, they blow from warmer land to cooler 
water. Some valley-breezes give rise to heavy showers. 

Variation in rainfall. Some places which were once moist are now 
dry, as shown, for example, by petrified forests in the desert of south- 
western United States. It is believed that a similar change in the 
past has made large areas of central Asia, formerly inhabited, too 
dry to support more than the scantiest population. In most places, 
the rainfall of corresponding months or seasons is rarely the same 
from year to year. These temporary variations are important 
factors (i) in floods, which in some cases cause great damage to prop- 
erty and heavy loss of life (p. 366), and (2) in droughts, which frequently 
result in even greater loss through damage to crops, and in some 
countries, as India and China, through deaths from famine. The 
United States, fortunately, rarely suffers from widespread failure of 
rain. Australia, on the other hand, has more than once been crippled 
by long-continued, severe droughts. In the United States, it has been 
shown that, with other conditions equal, the yield of corn depends 
directly on the amount of rain falling in June and July. When 
the amount is small, the crop is short. Other crops show similar 
close relation to rainfall. The importance of good crops to the 
prosperity of the country indicates that relative reliability of rainfall 
is a great national asset. 









CLIMATIC FACTORS: PRESSURE AND WIND 12 = 



Questions 

1. What effect do high altitudes have on the power of a steam engine? 

2. What weather conditions might indicate whether the pressure is high or 
low? 

3. Explain fully the effects on men (1) of a brisk wind, and (2) of calm air, 
in summer, in Louisiana. The same for winter. 

4. Why are the westerly and the trade- winds appropriately called planetary 
winds? 

5. Explain the significance of the data given in the table on page 115. 

6. On which side of Lake Michigan is the lake-breeze stronger in summer? 
Why? 

7. At what time of year would seasonal winds from Lake Michigan be most 
felt in Chicago? 

8. How much force is exerted on the side of a house 60 feet long by 25 feet 
high, when a wind is blowing go miles an hour? - 

9. How do seasonal (ocean-continent) winds affect the temperature of the 
east coast of North America in summer? In winter? How do they affect the 
west coast at the two seasons? 

10. Is the force of a wind which has a velocity of 20 miles an hour likely to be 
greater in summer or in winter at the same place? Why? 

11. In general, are winds stronger in California in winter or summer? Why? 

12. Why are the most desirable residential quarters of many manufacturing 
centers in the United States located to the west and northwest of the city? 

13. Suggest reasons why many coastal districts have more rain in winter than 
in summer; why the reverse is true for most continental interiors. 

14. Name the kinds of vegetation which you would expect to find at an alti- 
tude of 7,000 feet in the middle of the Sahara. 

15. In what portions of the world would power from the wind be most reliable? 
In what portions of the land areas? Why? Where is it most likely to be utilized 
by man? 

References 

Davis: Elementary Meteorology, Chs. VI, VII, XII. (Boston, 1894.) 
Greely: Rainfall Types in the United States, in Nat. Geog. Mag., Vol. V, 

PP- 45-58. 

Hann: Handbook of Climatology, Ch. XIII. (New York, 1903.) 

Henry: Rainfall of the United States, Weather Bureau Bull. D. 

Moore: Descriptive Meteorology, Ch. IX. (New York, 1910.) 

Page, Jas.: The Sailing Ship and the Panama Canal, in Nat. Geog. Mag., 

Vol. XV, pp. 167-175. 

Smith, J. W. : The Relation of Precipitation to the Yield of Com, in Yearbook, 

Dept. of Agri., 1903, pp. 215-224. 



CHAPTER VIII 
STORMS AND WEATHER FORECASTING 

Weather Maps 

Irregular winds have been mentioned (pp. 117, 123) as important 
factors in the distribution of rainfall and in changes of temperature. 
Such winds are associated with local and temporary conditions of 
pressure. Temperature, wind, rainfall (or snowfall), and cloudiness 
are the important elements in the weather of any place for any given 
time. As these elements are combined in different ways from day 
to day, the weather varies. Weather changes are important in so 
many ways that it is desirable, if possible, to know beforehand what 
changes are likely to occur. Thus winds of great velocity are danger- 
ous to shipping at sea, and vessels, if warned of their approach,, may 
remain in port. A freezing temperature in spring or autumn may 
cause losses amounting to hundreds of thousands, or even millions 
of dollars; but if sufficient warning is given, it is possible in some cases 
to protect perishable crops. In these ways and many more, weather 
changes and weather forecasting affect everyday life. 

Since weather changes are associated directly with irregular winds, 
and these in turn depend on pressure, it is evident that weather 
forecasting must depend largely on a study of pressure conditions. 
Changes of pressure from day to day have much more to do with 
weather changes than anything else has. 

Isobaric lines (p. 104) and isothermal lines may be put on the 
same map, which may show also where the sun is shining, where it is 
cloudy, where it is raining, snowing, etc. Such a map is a weather 
map, and may be made for any region, to show the weather at any 
given time. Thus Fig. 70 is a weather map of the United States for 
January 9, 191 1. Like all weather maps, it shows (1) isobars (full 
lines); (2) the direction of the winds (shown by arrows); (3) the 
degree of cloudiness; (4) areas of precipitation; and (5) isotherms 
(broken lines). 

Weather maps for the United States are made by the Weather 

126 






STORMS AND WEATHER FORECASTING 



127 




128 ELEMENTS OF GEOGRAPHY 

Bureau, a branch of the Federal Department of Agriculture. They 
are prepared in the chief cities, where telegrams are received twice 
daily from numerous stations in different parts of the country. Each 
telegram tells the pressure, the temperature, the direction and velocity 
of the wind, the cloudiness, and the rainfall at the station whence the 
telegram is sent. These stations are established and maintained by 
the Government. 

Explanation of the Map 

(i) Isobars. The isobars of the map (Fig. 70) show a range of 
pressure from 30.4 inches in the area centering in the Mississippi 
Valley, to 29.4 in Maine, and 29.2 in Washington. The pressure 
is more than 30 inches in the central part of the country, and less 
than 30 inches on both the Atlantic and Pacific coasts. 

The isobar of 30.4 in the central part of the United States is a 
closed line. The center of this high-pressure area is marked "high" 
(p. 102). West and east of the high the pressure decreases steadily 
toward the coasts, where there are centers of low pressure, marked 
"low" (p. 102). The minimum pressure in the low near the Pacific 
coast (29.2) is less than that in the low over Maine (29.4). Atmos- 
pheric pressures generally are unequal in different parts of the 
country. Hence most weather maps show both lows and highs, or 
at least one of each. 

(2) Winds. Wherever barometric pressures are unequal, isobaric 
surfaces are uneven and winds are the result. The arrows on a 
weather map show the direction of the winds. On January 9, 191 1 
(Fig. 70), winds were blowing away from the high and toward the 
lows. The movements of air out from an area of high pressure con- 
stitute an anticyclone, and the movements in toward an area of low 
pressure constitute a cyclone. A cyclone is one type of a storm. The 
winds in a cyclone are not always strong — rarely strong enough to 
be destructive. The violent wind-storms, popularly called cyclones, 
should be called tornadoes. 

Winds do not blow straight out from the anticyclonic centers, nor 
straight in toward the cyclonic centers. They may start straight out 
from the center of each high, but in the northern hemisphere they are 
turned (deflected) toward the right (right-hand half of Fig. 71, N), as 
most of the arrows about the anticyclone (Fig. 70) show. Similarly, 
the winds which blow toward the cyclonic centers do not blow straight 
toward them, but are deflected a little to the right in the northern 
hemisphere, as most of the arrows about the lows (Fig. 70) show. In 



STORMS AND WEATHER FORECASTING 



129 



the southern hemisphere, the winds are turned to the left instead of 
to the right (Fig. 71, S). 

The weather map tells nothing directly about actual wind veloci- 
ties. On government maps, this information appears in a table of 
data printed on the mar- 
gin. But the strength of 
the winds at various points 
may be inferred from the 
map. The distance from 
the center of the low in 
the east (Fig. 70) to Lake 
Michigan is about 800 
miles. The difference in 
pressure is about .9 inch. 
This would cause a wind 
of about 30 miles an hour 
— a high wind — between 
these points. In general, 
the gradient is high and 
the winds strong where 
isobars are crowded. 

As air moves in toward 
the center of a cyclone, it 

also moves spirally up. This upward movement has an important 
effect on precipitation (p. 123). The upward and outward course of 
the air in a cyclone is shown in Fig. 72, which represents a vertical sec- 




Fig. 71. Diagrams to show the circulation 
of air about a low, L, and a high, If, in the 
northern hemisphere (N) and the southern hem- 
isphere (S). 



■ 




























* > 


r 




















yy 


S* „ 


■* -*■ 


-»■ 


















/ y . 


S yS , 




/^ 


^^ ^ 










__ — -" 


/ y , 


'/ / 


/ / 


/ . 


-" / 


" s 










^ 


y s 


/ / / 


/ 


/ / 


/ 


( 












' y , 


/ / 




( 


V. 


y 












K ^ 


/ / 


\ 


v - 
















—-- ^ 


- / 


\ 


^ 




















V 












Wetf. 






" 












Scat. 





Fig. 72. Diagram illustrating the general movement of air currents in a 
cyclone of middle latitudes. The upper air moves mainly toward the east, in 
the direction of the prevailing winds. 

tion of a cyclone. The outflow above is chiefly to the eastward, the 

direction toward which the prevailing winds of middle latitudes blow. 

(3) Cloudiness and precipitation. An open circle on the shaft 

of an arrow (Fig. 70) indicates clear skies, a half-blackened circle (as 



i 3 o ELEMENTS OF GEOGRAPHY 



Hp 



in Wyoming) shows that the sky is partly cloudy, while a black circle 
(as in Montana) indicates general cloudiness. Cloudiness is estimated 
by the weather observers. If less than three-tenths of the sky is 
covered by clouds, the observer records clear; if from three- tenths to 
seven- tenths, the record is partly cloudy; if over seven-tenths, cloudy. 
An R on the shaft of an arrow (as in California) indicates rain, and 
an 5 1 in the circle on the shaft of the arrow (as in New York) shows 
that snow is falling. The map tells nothing about actual amounts 
of precipitation, but they are given in the printed table with the 
other data for each station. 

(4) Temperature. As indicated above, the broken lines of a 
weather map are isotherms. 

The isotherms of Fig. 70 show two distinct features: (1) they have 
little relation to parallels, and (2) the isotherms bend northward 
where the pressure is low, and southward where the pressure is high. 
This last feature is shown in most of the weather maps which follow; 
but on many of them the isotherms follow the parallels more closely 
than in Fig. 70. 

Cyclones and Anticyclones 

Characteristics of highs and lows. The highs and lows are 
sometimes much more pronounced than those shown in Fig. 70. In 
Fig. 73 the low is more pronounced, the pressure ranging from 29 at 
the center, to 30.1 in the East, and to 30.5 in the West. So great a 
range of pressure within the United States is not common. The iso- 
bars are closer together in this figure than in Fig. 70, and therefore 
indicate stronger winds. Cloudy skies prevail in the southeastern 
part of the cyclone. 

Highs as well as lows may have great area. Fig. 74 shows a high, 
or anticyclone, more than 2,000 miles across, with a great range of 
pressure. The isotherms of this chart, like those of the preceding, 
stand in very definite relations to the isobars. Denver, in the anti- 
cyclone (temperature — 10°), is about 30 colder than the southern part 
of Maine, which is 3 farther north, but on the western border of a 
cyclone. 

Near centers of low pressure, precipitation takes place in many 
cases, while around centers of high pressure there is, as a rule, an 
absence of precipitation. The chief reason for rainfall or snowfall 
about a low is that the inflowing air produces an upward spiral cur- 
rent, and the rising air expands and is cooled (p. 92), and so gives 
up some of its moisture. In the northern hemisphere, southerly 



STORMS AND WEATHER FORECASTING 131 




Fig. 73. Weather map for January 16, 1901, showing a very pronounced low. 




Fig. 74. Weather map for December 9, 1898, showing a high of great size. 



i 3 2 ELEMENTS OF GEOGRAPHY 

winds to the southeast of storm centers are, in general, blowing from 
warmer to cooler places, and this may result in precipitation. The 
prevailing winds which influence the direction of outflow in the 
upper part of a cyclone (Fig. 72) tend to carry the rainfall to the 
east of its center. 

This circulation of winds around cyclonic areas is the real factor 
in drawing moist air northward from the Gulf of Mexico, and in 
giving abundant rainfall east of the Mississippi River. 

In an anticyclone there is a descending spiral movement of air. 
The descending air comes from an altitude where the air is colder than 
that at the bottom of the atmosphere, and hence brings a low temper- 
ature. Winds from anticyclones generally bring clear weather, but 
cold air moving down and out from an anticyclone may mingle with 
warm air about it, so as to cause some of the moisture of the latter 
to condense, giving rise to clouds, or even to precipitation. 

Movements of cyclones and anticyclones. Highs and lows do 
not remain in the same place from day to day. This is shown by 
Figs. 75-78, which are the weather maps of four successive days. In 
these figures precipitation is shown by shading. 

In Fig. 75 there is (1) a low along the Atlantic coast; (2) a high 
central over Iowa; (3) a feeble low north of Montana; and (4) a high 
in Oregon. The map of the succeeding day (Fig. 76) shows (1) that 
the low of the St. Lawrence Gulf has disappeared (moved to the east) ; 
(2) that the high of the Interior has moved to West Virginia; (3) that 
the low which was north of Montana has moved to Dakota; while (4) 
the high of the Oregon coast remains about where it was. The map 
of the next day (Fig. 77) shows (1) that the high of the Virginias has 
moved on, but not so far as on the preceding day; (2) that the low 
which was over North Dakota is now north of Lake Superior; (3) 
that the high of Oregon has moved east to Idaho and Montana; and 
(4) that a weak low has developed in Oklahoma. The map of the 
27th (Fig. 78) shows (1) that the high which was over the Virginias 
has disappeared to the east; (2) that the low which was north of Lake 
Superior is now north of Lake Ontario; (3) that the high of Montana 
has moved southeast to Kansas; (4) that the weak low which was 
in Oklahoma has disappeared; and (5) that another feeble low has 
appeared in southern California. 

The rate of progress of a storm is not the same as the velocity of 
its winds. The velocity of the wind depends on the isobaric gradients. 
A weak cyclone, that is, a cyclone in which differences of pressure are 



STORMS AND WEATHER FORECASTING 133 



1 25^ 120 17 115° . 110° 105° 100° 95° 90° 85° 80° 75° 70° 65^ 




115° 110° 105° 100" 95° 90° 85° 



75° 70° 



Fig. 75. Weather map for September 24, 1903. The shading on this and 
succeeding maps indicates areas of precipitation during the preceding 24 hours. 



125° 120° 115° 110° 105° 100' 95 



75° . 70° 65° 




115° 110° 



Fig. 76. Weather map for September 25, 1903. 



134 



ELEMENTS OF GEOGRAPHY 



_ 



110° 105° 100' 95° 90° 85° 80° 75° 70" 




115° 110° 105° 100° 95° 90° §5" 



Fig. 77. Weather map for September 26, 1903. 



125' 120" 115" 110' 105" 100" 95" 90" 85" 80" 75' 70' 65" 




°3O03^ 




^-^i-^k^Wf" 


/!r"~~~~~^ it 4*'/ — V/v* 


JtmLJ 

532 


Pp 


v\ 1 


TO 


St»-'" \ 

^^T \ U' 80 ° 1 1 




9 ^PT^x 


*5al«eston 






1 i 






"'■ 80 I 60.-.. LgMVIM CO 1.1 


115" 110" 105" 100" 95" 90" 85" 75" 70" 



Fig. 78. Weather map for September 27, 1903. 



STORMS AND WEATHER FORECASTING 



i35 



not great, gives rise to weak winds, even though the center of the 
storm moves rapidly. A strong cyclone, that is, one in which the 
differences of pressure are great, gives rise to strong winds, even 
though the cyclone itself may move forward slowly. 

The rate at which cyclones move varies with the season, the 
average being about 37 miles per hour in winter and 22 in summer. 
Storms may move at twice these rates, however, or at less than half 
their usual speed. 




Fig. 79. Chart showing the mean tracks of cyclones (light lines), anticyclones 
(heavy lines), and average daily movement (broken lines). 



The course of a cyclone may be shown on a single map, as in 
Fig. 70. The row of arrows shows that the low of Maine has moved 
from western Canada. 

The mean tracks of cyclones and anticyclones for the United 
States are shown in Fig. 79. The broken lines on this map, marked 
1 day, 2 days, 3 days, and 4 days, show the average daily progress 
of storms which come from the northwest. 

Some anticyclones enter the United States from the Pacific, while 
others start north and northwest of Montana, or, at any rate, are first 
reported from there. Cyclones originate in various places. More 
of them originate near the places where anticyclones start than in 



136 ELEMENTS OF GEOGRAPHY 



asm. 



other places; but many appear first in Colorado, the Great Basin, 
Texas, and elsewhere. 

The passage of a cyclone or anticyclone involves a change in the 
direction of the wind, and usually also changes of temperature 
humidity, and cloudiness. Thus in Fig. 76 the wind at St. Paul i 
southeasterly, though this city is in the zone of westerly winds. Th 
next day, after the storm center has moved forward to a positio 
northeast of St. Paul (Fig. 77), the wind is northwesterly. An east 
wind is often the first sign of an approaching cyclone; and since 
many cyclones bring rain, an east wind is generally taken as a sign 
of approaching rain throughout much of the United States. 

. Cyclones are, on the whole, more frequent and better developed 
in winter than in summer. They do not affect the air to great heights. 
Even when the great whirl or eddy is 2,000 miles across, as is sometimes 
the case, its height (depth) is rarely more than 4 or 5 miles. The 
origin of the cyclones and anticyclones of middle latitudes is not well 
understood. 

Winds and temperatures incidental to cyclones and anti- 
cyclones. During the passage of a cyclone, the air to the southeast 
of the storm center is drawn from warmer (lower) to cooler (higher) 
latitudes. In midsummer this often gives rise to a hot wave, though 
not all hot waves are associated closely with cyclones. Similar winds 
are known as the sirocco in the western Mediterranean region. In 
eastern United States, numerous sunstrokes and deaths from heat 
prostration accompany some hot waves in their progress across the 
country. In Mediterranean countries, the sirocco often combines 
high temperature and extreme humidity. Such conditions are very 
trying, as indicated by a Spanish proverb: "Ask no favor while 
the solano (sirocco) blows." The famous brick fielder of Australia, 
and the zonda of Argentina are winds of this same origin, and similar 
winds have other names elsewhere. 

Air to the northwest of a cyclone moves from cooler (higher) to 
warmer (lower) latitudes. In winter, this may give rise to cold 
waves. These cold winds are known as northers in the southern part 
of the United States, and sometimes as blizzards in the northern 
part, though this name usually implies heavy snowfall and high wind, 
as well as low temperature. Fig. 80 shows the weather map for 
January 3, 1896. The isotherms bend southward about the high, 
so that central Texas and Montreal have about the same tempera- 
ture. On the following day (Fig. 81) a freezing temperature has 



\ 



STORMS AND WEATHER FORECASTING 137 



43 
40 

3d 

25 


125° 120" 115° HO" 105" 100° 95° 90° 85" 80° 75° , 70" 65" 


T\/\ iM^^&h^^ 


2 


S-2P° r^-t U— ~ /v ft? *\^\^&\iS? 
KJebl&H — ' — \^-r\//l c ^- 3 °°'' 


U 


c^ioHFiHl' * -via lxJ 50° \ 




y ^^^^^^ 


5^% 




%«W \ \ 




«o° 






1 Y ' \ 1 } 




KeylWest^ 1 1 1 


115° 110° 105° 100° 95° 90° 85° 80° 75° 70° 



Fig. 8o. Map showing the cold wave of January 3,1! 



125° 120° 115° 110° 105° 100° 95° 90° 85° , 80° 75° 70° 65' 




115° 110" 105° 100° 95° 90° 85° 



Fig. 8i. Map for January 4, 1896, showing the progress of the cold wave 
of Fig. 80. 



138 ELEMENTS OF GEOGRAPHY 



ng 



been carried down to the orange groves of northern Florida. Among 
the other names by which similar cold winds are known are mistral 
in southern France, bora along the Adriatic, southerly burster in 
Australia, and pampero in Argentina. 

When warm, moist air is forced up over mountains, it precipitates 
some of its moisture (p. 123). The precipitation sets free heat, so 
that the rising air is cooled much less than it would be otherwise. 
Beyond the crest of the mountains it descends, and is warmed in the 
process. It is warmed much more (often twice as much) in the 
descent than it was cooled in the ascent. It may, therefore, descend 
as a hot wind. Such winds are known as foehn winds in Switzerland, 
and as chinook winds in the United States, especially just east of the 
Rocky Mountains. 

These winds may be beneficial or harmful. Thus the chinook winds temper 
the rigorous winters of certain parts of the northwestern states and the Canadian 
provinces east of the mountains. They frequently evaporate a foot or more of 
snow in a few hours. For this reason they are sometimes called "snow-eaters." 
These winds make winter grazing possible over large areas which otherwise would 
be covered heavily with snow. In the province of Alberta the chinook has been 
declared to be "the grand characteristic of the climate as a whole, that on which 
the weather hinges." These winds sometimes develop with great suddenness. 
At Fort Assiniboine, Montana, on January 19, 1892, the temperature rose 43 F. 
(from -5.5° to 37.5°), in fifteen minutes, under the influence of the chinook wind. 
In other cases the temperature has been known to rise 8o° in six or eight hours. 

The chinook winds of summer are sometimes so hot and drying as to wither 
vegetation, and occasionally to destroy crops. The Swiss foehn is so dry that 
general conflagrations among the wooden cottages are feared greatly, and in 
some villages all domestic fires are extinguished while the foehn blows. 

Tropical cyclones. Cyclones sometimes start in tropical regions, 
and follow courses very different from those of the cyclones of middle 
latitudes. The cyclones of this class which reach North America 
usually originate in the West Indies, and are most common in late 
summer and early autumn. They follow a northwesterly course 
until the latitude of Florida is reached. Here they commonly turn 
to the northward, and later to the northeastward, following the 
Atlantic coast. The heavy line of Fig. 82 shows the average path of 
tropical cyclones for the months of August, September, and October, 
for the years 1878 to 1900. 

Tropical cyclones (hurricanes) are stronger than those of intermedi- 
ate latitudes ; that is, the gradient and the winds are higher, the velocity 
of the wind in many cases exceeding 100 miles an hour. Many of 
these cyclones do great damage along the coast, both to shipping 



STORMS AND WEATHER FORECASTING 



139 



and to low lands near the water. The great storm at Galveston, 
in September, 1900, resulted in a loss of 6,000 lives, and damage to 
property estimated at more than $30,000,000. Fig. 83 shows (1) the 
course of the storm before it reached Galveston and after leaving it, 
and (2) the rate of its progress. The strength of the storm was 
exceptional, and its course unusual, as will be seen by comparing 
Fig. 83 with Fig. 82. Much of the destruction was due to water 
driven by the high winds over the low island on which Galveston 




Fig. 82. Course of West Indian storms for August-October, 1878-1900. 
The heavy line indicates the mean track. 



stands. An expensive sea-wall (Figs. 84 and 85) has since been built, 
and the level of the city raised, to prevent the recurrence of such a 
disaster. 

In September, 1906, a West Indian hurricane swept the Gulf coast of 
Florida and Alabama, and then passed inland, with damage to shipping and crops 
estimated at 15 to 25 millions of dollars. These tropical storms are so violent that 
any vessel, except the staunchest steamship, once within the storm's grasp, rarely 
escapes. For this reason there has been much careful study of these storms. 
Elaborate sailing directions, giving instructions how to escape from them, are 
now an essential part of the equipment of every vessel frequenting the oceans 
where tropical cyclones occur. 



140 



ELEMENTS OF GEOGRAPHY 




STORMS AND WEATHER FORECASTING 



141 



In the Atlantic, tropical cyclones occur north of the equator, 
though not south of it; in the Pacific, they occur both north and south. 
They occur in the later part of the hot season, and consequently are 




Fig. 84. Portion of the sea-wall built to protect Galveston. 




Fig. 85. A cross-section of the Galveston sea-wall, showing plan of construc- 
tion and relative dimensions. The right-hand side faces the sea. 



142 



ELEMENTS OF GEOGRAPHY 



believed to be strong convection (p. 61) currents. The tropical 
cyclones of the North Pacific, called typhoons, start somewhere east 
of the Philippines, and sweep the coast of China (Fig. 86). Tropical 

cyclones are much less 
frequent than cyclones 
of middle latitudes; 
otherwise, the portions 
of the tropics affected 
would be almost unin- 
habitable. Islands 
which lie near cyclone 
tracks suffer severely. 
Porto Rico, for exam- 
ple, has been devas- 
tated five times within 
the last century (1825, 
1837, 1867, 1899, and 
19 10). The storm of 
1899 was probably the 
worst, and the entire 
island was crippled. 
Coffee, sugar-cane, and 
tobacco crops were de- 
stroyed almost com- 
pletely, more than 3 ,300 
Fig. 86. Typhoon tracks. (Herbertson.) lives were lost, and the 

property damage was 
estimated to be not less than $35,000,000. During this storm 23 
inches of rain fell in 24 hours. 




Weather Forecasting 

Weather predictions. Weather predictions are based on the 
facts shown on weather maps. As a rule, official predictions are 
made only for the 36 or 48 hours immediately following the hour when 
the map is made. Take, for example, the map of the 25th of Septem- 
ber, 1903 (Fig. 76). Rain accompanies the cyclone which is central 
over Dakota. Since this storm has, for the last 24 hours, been moving 
a little south of east at the rate of about 40 miles an hour, it is fair to 
presume that it will move in this same general direction at a similar 



STORMS AND WEATHER FORECASTING 143 

rate for the next 24 hours. If, in this time, it advances to the Lake 
Superior region, it probably will bring with it weather similar to that 
which it is now giving to the region where it occurs. Hence, on the 
25th, the prediction might be made that rain is to be expected in 
about 24 hours in the region about the head of Lake Superior. 

On the 26th the prediction might be made that the low which is 
central north of Lake Superior (Fig. 77) will move on to the Gulf of 
St. Lawrence by the succeeding day, and that increasing cloudiness 
and rain will accompany it. Rain for the region about Lake Huron 
and the area east of it may, therefore, be predicted for the 27th. The 
chart for that day (Fig. 78) shows that the area of precipitation 
extends far to the south. The preceding map had shown some cloudi- 
ness in this region, but had afforded no warrant for the prediction 
of such an area of precipitation as appears on the map of the 27 th. 

Temperature changes as well as changes in cloudiness and precipi- 
tation may be predicted. Thus in Fig. 75 the isotherm of 50 bends 
southward notably in the high, central over Iowa. As the high moves 
east, it will probably carry the low temperature with it. Hence 
it is safe to predict that the temperature will fall in the area into 
which the anticyclone is to move. The map of the succeeding day 
(Fig. 76) shows that the temperature of western Virginia has fallen 
from about 6o° to about 40 along the path of the high, while areas 
much farther north are warmer. 

Fig. 76 also shows that North Dakota and Alberta have a tempera- 
ture of 50 , that is, a temperature io° warmer than that of western 
Virginia. It will be noted, too, that the relatively high temperature 
of Dakota, Montana, and Alberta goes with a low. As the cyclone 
moves eastward, the temperature along its path will probably rise. 
This is shown by the map of the next day (Fig. 77), which shows a 
temperature of about 50 north of Lake Superior. The same map 
shows how the isotherm of 40 bends to the southward in front of the 
high which is central over western Montana. As the high of Montana 
moves eastward, it will be likely to carry a low temperature with it. 
From this map, therefore, it may be predicted that the temperature 
in Nebraska, Kansas, Iowa, and Missouri will fall. 

The time when the rain which a storm may bring to any given 
place will fall is calculated from the rate at which the storm is 
moving. In the same way, the prediction of the time of arrival of a 
cold wave which an anticyclone may bring is based on the rate of 
progress of the anticyclone. This rate is known in advance by 



144 ELEMENTS OF GEOGRAPHY 



be 



telegraphic reports. Predictions concerning the weather may be 
made more readily for the central and eastern parts of the United 
States than for the western part, for the storms have been under 
observation longer before they reach the central and eastern states. 

Long-range weather predictions. Attempts often are made 
to predict weather changes and conditions for a whole year, or for 
the different seasons. Without exception, these so-called "predic- 
tions," based on the color of goose-bones, the thickness of fur of ani- 
mals, the state of the weather on certain "sign days," and so on, are 
mere guesses. Like all guesses, they sometimes hit, but more often 
miss. For all practical purposes, they are worthless. 

There is no doubt that forecasts of the weather for longer intervals 
would be immensely valuable if they could be made with accuracy. 
Recently the Weather Bureau has attempted forecasts for a period 
of a week in advance, and in some cases has met with a fair degree of 
success. These long-range forecasts depend on a study of pressure 
conditions over most of North America, and as far as possible over 
the adjacent oceans. As more comes to be known concerning the 
origin of cyclones and anticyclones, their relation to pressure condi- 
tions and to the upper air, and as larger areas are brought under 
observation, it seems likely that fairly good forecasts can be made 
for periods of several days. 

Failure of weather predictions. Weather predictions, even 
for short intervals, often fail. The reasons are many, among them 
the following: 

(i) Cyclones and anticyclones sometimes depart widely from the 
courses they commonly take. Thus a storm may be in line for St. 
Paul, to which it is expected to bring rain and a rising temperature; 
but instead of keeping its course, it may turn off to the northward, 
and the rain which was predicted for that city falls farther north. 

(2) Storms change their rate of advance, and So arrive earlier or 
later than predicted. The high of Oregon (Fig. 75) did not advance 
for a day (Fig. 76), and so failed to bring the expected changes to the 
area east of it. 

(3) Again, storms sometimes appear and disappear without 
warning. Fig. 77 shows a low over Oklahoma, of which there had 
been no indication on the 25th. Fig. 78 shows that this low has 
disappeared. 

(4) A storm sometimes changes its character, becoming weaker 
or stronger, etc. Figs. 87 and 88 afford an illustration. Nothing 






STORMS AND WEATHER FORECASTING 



145 



in the map of the 20th would warrant the prediction of the conditions 
of weather shown on the map of the 21st. 

(5) Sometimes predictions are based on imperfect data. On some 
weather maps the letter M appears in various places. This means 
that reports from the stations where the M appears are missing. If 
many reports are missing, the map is imperfect, but the forecaster 
must use such data as he has, as well as he may, and issue a map. 




Fig. 87. Weather map for January 20, 1895. 

(6) In some situations storms are subject to many freaks. This 
is the case, for example, at Chicago, where Lake Michigan modifies 
temperature and air currents. 

Forecasters, like other men, make mistakes, but when they have 
to work with so many uncertain elements, it is not strange that their 
predictions sometimes are wrong, and one mistake is likely to be 
remembered longer than many correct forecasts. 

Value of weather forecasts. In spite of all mistakes, the 
warnings of storms, floods, cold waves, etc., sent out by the Weather 
Bureau, have been of great benefit. The value of this service is not 



146 



ELEMENTS OF GEOGRAPHY 



always duly appreciated, and much less is heard of it than would 
have been heard of the losses which would have resulted if warnings 
hacLnot been given. Unfortunately, it is not always possible to 
devise protection against the evils of which the Weather Bureau gives 
warning. It has been estimated that property valued at $15,000,000 
was saved in 1897 by warnings of impending floods. In 1903-4 the 
estimated saving was $1,000,000. 




Fig. 88. Weather map for January 21, 1895, showing, the storm of the preced- 
ing day greatly increased in intensity. 

Shipping interests are served by warnings of storms. Thus, in September, 
1903, vessels valued at $585,000 were held in ports temporarily, along the coast of 
Florida, by storm warnings. The loss of the Boston steamship City of Portland, 
with all on board, in the great storm of November 28, 1898, was due to a failure 
to heed storm warnings which kept all other craft in port. 

Agricultural interests also are served by warnings of storms and of "cold 
waves," and especially of frosts. Warnings led to the protection of $1,000,000 
worth of fruit about Jacksonville, Florida, in 1901, with an estimated saving of 
half this amount. Other warnings of cold in 1901 were estimated to have been the 
means of saving more then $3,000,000 worth of property. Fruit and truck farming 
are the phases of agricultural work served most effectively in this way. Shipments 






STORMS AND WEATHER FORECASTING 



147 



of perishable products, like most fruits, may be damaged badly if freezing tempera- 
tures are encountered unexpectedly in transit. Merchants handling such products 
are saved much trouble and inconvenience by information from the Weather 
Bureau concerning the temperatures for which their shipments must be prepared. 

The annual saving of property in these various ways exceeds, 
several times over, the total cost of the Weather Bureau. 



Local Storms 

Thunder-storms. Thunder-storms are frequent in the United 
States. They are most common in warm regions, and in warm 
seasons. Further, they are most common on days which are unusually 
warm, and during the warmer parts of these days; but there are 
occasional thunder-storms in the winter, and there are thunder- 
storms at night. 

The first indication of a thunder-storm is usually a large cumulo- 
nimbus cloud (Fig. 89), which, in the zone of the westerly winds, 




Fig. 89. Vertical section of- a thunder-storm which is moving toward the 
right. (Koppen.) 



generally appears in the west. It moves eastward, and as it reaches 
the place of the observer, there is usually a smart breeze, or thunder- 
squall, rushing out before it. Shortly after the squall the rain begins 
to fall. The rainfall may be heavy, and the drops large, but the 
downpour does not usually last more than an hour, and in many cases 
much less. A second thunder-storm sometimes follows close upon 
the first, thus prolonging the period of rainfall. When a thunder- 
storm has moved on to the east, the air is, in many cases, notably 
cooler and fresher, and the barometer distinctly higher. But when 
the sun reappears quickly, rapid evaporation may raise the humidity 
to a point which makes the air extremely oppressive. Hence a 



148 ELEMENTS OF GEOGRAPHY 

thunder-storm cannot always be counted on to relieve the heat of a 
damp, midsummer day. 

Lightning is due to the discharge of electricity from one part of a cloud to 
another, or from one cloud to another, or from the cloud to the ground. When 
lightning discharges come toward the ground, they seek exposed objects in 
some cases and cause loss of property, chiefly through fire, and occasional loss of 
life. The total of both, however, for a year, is much smaller than that from 
fires due to other causes. Buildings may be protected from lightning by care- 
fully erected lightning rods; but rods carelessly constructed or adjusted are 
worse than none. 

The flash of lightning is followed by thunder, the noise being due to vibrations 
in the air caused by the electrical discharge. Thunder has been compared to the 
noise which follows the explosion of a rocket or the cracking of a whip. 

In middle latitudes, most thunder-storms occur during the passage 
of cyclones, though they do not accompany all cyclones. They 
are more common on the south sides of cyclones than elsewhere, and 
many of them occur at a considerable distance from the center of the 
main storm. In middle latitudes, most thunder-storms move from 
west to east, while in the zone of trade-winds they move from east 
to west. In both cases they move with the prevailing winds. 

Much of the precipitation from summer cyclones is connected with thunder- 
storms. Hence localities having most of their rain during the warm season depend 
largely on thunder-storms for moisture. This condition is characteristic of much 

of central and eastern United States. 
Not infrequently violent thunder-storms 
give precipitation in the form of hail. 
The exact conditions producing hail are 
not known, but in regions subject to fre- 
quent hailstorms, as some parts of Medi- 
terranean Europe, the annual damage is 
heavy. 

Fig. 90. Shape of thunder-storm The forward movement of thunder- 

in ground plan, illustrating its growth storms is commonly 20 to 50 miles an 
and change as it progresses. (Waldo.) hour. Many of them spread and become 

weaker as they move forward (Fig. 90). 
Most of them disappear before they have traveled far. The period of a thunder- 
storm is usually much shorter than that of the cyclone which it accompanies. 

It sometimes happens that lightning at a great distance lights the clouds over 
a region where the electric discharge itself cannot be seen. This lighting of the 
clouds is often called heat lightning, because it is more commonly seen in hot weather 
than at other times. The rainbows which accompany or follow many thunder- 
storms are due to the effects of the drops of water in the atmosphere as the sun's 
rays pass through them. 

Whirlwinds. Ascending whirls of air are seen frequently on 
hot days. They are most distinct in dusty regions, for there the 




STORMS AND WEATHER FORECASTING 149 

dust which is swept up makes the whirl conspicuous. From a given 
point in the Mojave Desert, in California, as many as eight or ten 
of these whirls, some of them rather large, have been seen at one time 
on a hot summer day. Several are occasionally in sight at once 
from a train as it passes through this region in summer. The whirl- 
winds probably are caused by the excessive heating of the air at some 
point, and this excessive heating gives rise to a sharp convection cur- 
rent. The whirl moves on for a time with the prevailing wind, but 
soon dies out. The dreaded simoons of the Arabian and African 
deserts are strongly developed, dust-laden whirlwinds. 

In humid regions, whirlwinds do not usually appear to extend 
up to any considerable height; but in desert regions they may reach 
heights of 1,000 feet or more, as shown by the columns of dust. The 
rise is sometimes so great that the air is expanded and cooled enough 
to cause condensation of even the small amount of moisture contained 
in the desert air. Smart showers may then occur. Showers of this 
sort are likely to be of short duration, but the rainfall may be 
very heavy. If exceptionally heavy, such rains are known as cloud- 
bursts. In such a storm, in the summer of 1898, rain enough fell in 
a few minutes, in the vicinity of Bagdad, in the Mojave Desert of 
California, to occasion serious washouts along the railroad for miles. 
A cloudburst at Clifton, S. C, June 6, 1903, caused the loss of more than 
50 lives, and property damage to the estimated extent of $3,500,000. 
In desert regions, the water which starts to fall from the rising and 
expanding air is sometimes evaporated before it reaches the ground. 
Such "suspended" showers may be seen often in Arizona in August. 

Tornadoes. When a convection current is very strong, and has a 
very small diameter, the whirl becomes so intense in some cases as to 
cause great destruction. A whirling storm of this sort is a tornado. 
Tornadoes, like thunder-storms and whirlwinds, are phenomena 
of hot weather. They occur in the United States in the hot days of 
spring and early summer, appearing earlier in the south, and later in 
the north. This relation of tornadoes to the warm season is indicated 
by the fact that of 600 recorded tornadoes, nearly two-thirds occurred 
in the four months, April to July, and less than one-eighth in the 
four months, November to February. They are rather less abundant 
in the later part of the summer than in the earlier part. They are 
more likely to occur in a cyclone than in an anticyclone. Tornadoes 
are associated in most cases with hot days, and with the warmest 
part of the day. 



i5° 



ELEMENTS OF GEOGRAPHY 



The atmospheric pressure in the center of the tornado is usually 
much lower than in the center of a cyclone. In a very strong tornado, 
the pressure at the center may be a fourth less than that of its sur- 
roundings. This is one reason why the tornado is so destructive. 
During its passage, the pressure may be reduced from the normal 
amount, 14.7 lbs. per square inch, to three-fourths of this, or to n lbs. 
per square inch. If such a tornado passes over a closed building in 
which the air pressure is 2,117 lbs. P er square foot, the pressure on the 
outside becomes 1,584 lbs. The walls are therefore pushed out with 
a force of 533 lbs. per square foot, and unless they are very strong, 
they will fall, as if the building had exploded. In some cases only 
the weaker parts, such as windows, yield. 

Not only is the pressure at the center of the tornado very low, but 
the area of this low pressure is very small. While a cyclone may be 
1 ,000 miles or more across, few tornadoes are more than a mile across. 
Most of them do not exceed 1,000 feet in diameter at the surface of 

the land, and many are only a 
few yards wide. 

The result is that the pres- 
sure gradient in a tornado is 
very much higher than in a 
cyclone, and the winds are vio- 
lent. Their velocities, estimated 
by the size and weight of the ob- 
jects moved, have been thought 
to reach 400 or 500 miles per 
hour. With this velocity, or 
even a velocity which is much 
less, destruction is great. Trees 
are overturned, buildings un- 
roofed or blown down, and 
bridges hurled from their foun- 
dations. 

A tornado is often seen first 
as a funnel-shaped cloud (Fig. 
91), the point of which may be 
far above the ground. As the funnel moves forward, its lower end 
may rise or fall. The cloud is due chiefly to the condensation of 
moisture in the sharp convection current, and the funnel shape is 
due to the expanding and spreading of the air as it rises. 




Fig. 91. Funnel-shaped cloud of a 
tornado, Solomon, Kas. (U. S. Weather 
Bureau.) 






STORMS AND WEATHER FORECASTING 151 

The tornado is, of all storms, the most destructive, but, in most 
cases, it has a very narrow track, and does not work destruction for 
a very great distance. After a short course of 15 to 30 miles, most 
tornadoes die out, or rise above the land. 

One of the most destructive, though not one of the most violent, tornadoes of 
recent times was that at St. Louis, May 27, 1896. It accompanied a thunder- 
storm in the southeastern part of a cyclone, central some distance northwest of 
the city. The wind velocity indicated by the instruments at the Weather Bureau 
office was 128 miles per hour at the time the anemometer was blown away. One 
of the extraordinary features of this storm was the fact that its base was about 30 
feet above the surface. Trees were twisted off at this level, and the principal 
destruction of houses was above the first floor. 

As in other tornadoes, the wind played many curious freaks. Single stones and 
bricks were picked out of walls, while the walls remained standing. In one case a 
pair of horses attached to a loaded wagon were blown away, though the wagon 
was not overturned. The destruction of property in and about St. Louis was 
estimated at about $13,000,000. 

A more violent tornado was that at Louisville on the 27th of March, 1890, 
just before nine o'clock in the evening. Many weak buildings were wrecked, 76 
persons were killed and about 200 injured in Louisville alone, and the loss of prop- 
erty was estimated at about $2,500,000. 

The number of tornadoes is probably not increasing even in the 
section of the central and lower Mississippi Valley where they occur 
most frequently. It is likely, however, that the increasing number 
of towns and villages in this district may mean greater loss from these 
storms. No device is likely to be of any use in preventing or breaking 
up tornadoes. Neither is tornado prediction practicable at present, 
on account of the impossibility of determining just where the narrow 
track will be, and the undesirability of sending out broadcast warn- 
ings. Hence, in spite of the fact that the weather map may show 
conditions favorable for tornadoes, they are not mentioned in the 
forecasts. 

In recent years, insurance of property against loss by tornado has 
become quite common in the states most affected, until at present 
the value of the property so insured is estimated at considerably over 
$500,000,000. It has been estimated that any given area in the 
tornado region the size of an average farm (say 160 acres) stands 1 
chance in about 1600 of being hit once in 100 years. Hence if tornado 
risks are distributed carefully, even such a disaster as at St. Louis 
would not wreck the insuring companies. 

Waterspouts. Waterspouts ,are tornadoes at sea. When the 
base of the upward spiral movement is at the surface of the water, 



1 52 ELEMENTS OF GEOGRAPHY 

sea-water may be drawn up to some extent by the ascending current. 
But the larger part of the water in a waterspout is probably formed 
by the condensation of the water vapor in the air, and not by the 
uplift of water from the sea. Waterspouts, however, are much less 
common than tornadoes on land, since water areas, as a rule, do not 
favor the development of the strong convectional currents essential 
for these storms. 

Questions 

i. From Fig. 70, p. 127, suggest reasons (1) for cloudiness along the Gulf 
coast and in Montana, (2) for the absence of cloudiness in Kansas, and (3) why 
the isotherms bend southward in Illinois. 

2. Explain the apparent contradiction in the fact that northeast winds, in 
most areas of the United States, are part of a storm coming from the west. 

3. Show by a series of diagrams, in their proper order, the weather changes 
which would take place at a given station on three successive days under the 
following conditions: (1) On the first day the storm center (low) is approaching 
from the southwest; (2) on the second day at noon the center is 200 miles away, 
directly to the south; (3) on the third day it has moved on in the normal direction, 
and at the normal rate. Diameter of the low, 1,000 miles. 

Make similar diagrams for a storm following a track 200 miles to the north of 
the station. 

4. At many places, cloudiness on the southwestern horizon, especially in the 
evening, is regarded as a sign of a storm the following day, and the appearance 
of clear sky on the northwestern horizon is regarded as evidence of the end of a 
storm. Give reasons for these beliefs. 

5. Formulate rules for forecasting- temperature when the weather map shows 
isotherms running (1) east and west, and far apart; (2) north and south, and close 
together. 

6. What basis in fact have the following weather proverbs: (1) "Too cold to 
snow." (2) " A white frost is a sign of a fair day to follow." (3) "Rainbow in the 
morning, sailors take warning; rainbow at night, the sailors delight." (4) "If 
the wind sets with the sun, there will be a frost." (5) "A mild, sunny day in winter 
is a weather breeder" (meaning that a storm will follow within 24-36 hours). 

7. Suggest other weather proverbs which you have heard, and show whether 
or not they have any basis of truth. 

8. Why are large dealers in grains, cotton, and tobacco interested in the daily 
weather map? 

9. Draw diagram (using isobars) of a West Indian hurricane off the coast of 
Florida, with a sailing vessel in the vicinity of the storm area. Trace the probable 
course of the ship if it sails with the wind. Remembering that the vessel can sail 
in any direction except against the wind, indicate the proper course for the ship to 
take to escape the storm when it is (1) to the east of the probable storm track; 
(2) west of the track; (3) directly in the path of the storm. 

10. Where do the storms originate (Fig. 79) which give rain to the agricultural 
regions south and west of Chicago? 






STORMS AND WEATHER FORECASTING 153 

11. Compare the effect of winter cyclones (see Fig. 79) on the weather of (1) 
New England, and (2) the Dakotas. 

12. Suggest some of the changes in the climate of the United States which 
would result (1) if the Rocky Mountains ran east and west, along the entire length 
of the Canadian boundary; (2) if the area of the Gulf of Mexico were land. 

13. What would be the effect of continued high pressure over the upper 
Mississippi Valley in summer? In winter? 



References 

Burrows: The Chinook Wind, in Jour, of Geog., Vol. II, pp. 124-135. 

Dexter: Weather Influences. (New York, 1904.) 

Garriott: The West Indian Hurricane of September 1-12, igoo, in Nat. Geog. 
Mag., Vol. XI, pp. 384-392. 

Garriott: West Indian Hurricanes; Weather Bur. Bull. No. 4. 

Garriott: Weather Folklore and Local Weather Signs; Weather Bur. Bull. 
No. 33. 

Grosvenor: Our Heralds of Storm and Flood, in Nat. Geog. Mag., Vol. XVIII, 
pp. 586-600. 

Moore: Descriptive Meteorology, Ch. XIII. (New York, 1910.) 

Moore: Forecasting the Weather and Storms, in Nat. Geog. Mag., Vol. XVI, 
pp. 255-305. 

. Ward: A Year of Weather and Trade in the United States, in Pop. Sci Mo., 
Vol. LXI, pp. 439-448. 



CHAPTER IX 
TROPICAL CLIMATE 

Distribution 

Extent of tropical regions. The tropical zone, as usually 
denned, is limited by the Tropic of Cancer on the north, and the Tropic 
of Capricorn on the south. Qther definitions of this zone have been 
suggested, as (i) the zone between the poleward limits of the trade- 
winds in the northern and southern hemispheres, and (2) the zone 
where the palm-tree grows naturally, the palm being taken as the 
type species of tropical vegetation (Fig. 92). While each of these 
definitions of the tropical zone has merit, the definition by parallels 
is used here, as being most precise and simple. The tropical zone 
covers about two-fifths the area of the earth. Within it, land and 
water are distributed very unequally. 

Land and water areas — Western Hemisphere. The tropical 
part of North America includes most of Mexico, all of Central America 
and the islands to the east, or about one-seventh of the area of the 
continent. This area supports- about one-sixth the people of the 
continent. If the tropical zone were defined by winds or by the distri- 
bution of palms, as suggested above, its area and population would be 
greater. North of the equator, the Gulf of Mexico and the Carib- 
bean Sea make a big expanse of water almost in the heart of the 
tropics, and these bodies of water are of great importance to the 
climate of the eastern half of the United States (p. 132), as well as 
to that of the lands to the south. 

South America contains the largest tropical land area in the West- 
ern Hemisphere, nearly three-fourths of it lying between the Carib- 
bean Sea and the Tropic of Capricorn. The tropical part of this con- 
tinent contains fully three-fourths of its population. Brazil, the 
largest country of South America, is almost wholly tropical (Fig. 92). 
Chile and Argentina are the only important countries of this con- 
tinent lying mainly outside this zone. 

Land and water areas — Eastern Hemisphere. Of the north- 
ern Continents of the Eastern Hemisphere, only the southern penin- 

i54 • 



TROPICAL CLIMATE 



155 



sulas of Asia and the islands associated 
with them are south of the Tropic of 
Cancer (Fig. 92). The tropical parts of 
Asia make only about one-fifth of its 
area, but they support fully half its pop- 
ulation. 

Africa occupies, in the eastern world, 
the same relative position that South 
America does in the western. Fully three- 
fourths of its area and two-thirds of its 
population are between the tropics of 
Cancer and Capricorn. Even those parts 
of Africa which lie outside the tropics 
have climatic conditions not greatly dif- 
ferent from those of the tropical parts of 
the continent. 

About half of Australia and one-fourth 
of its population are within the tropics, 
and the climate of the remaining half is 
not very different from that of the tropi- 
cal zone. 

Summary. About one-third of all the 
land — in round numbers, 17,000,000 
square miles — lies within the tropics. 
This third of the land supports about one- 
third the population of the earth, — in 
round numbers, 500,000,000 people. Much 
tropical land is desert, and much is covered 
with dense forests (Fig. 96). These parts 
are but sparsely populated, but the fertile 
and cultivated portions of this zone sup- 
port dense populations. In Java, for 
example, 30,000,000 people live in an 
area two-thirds the size of Pennsyl- 
vania. 

The area of ocean within the tropics 
is about 70,000,000 square miles. The 
large proportion of water in this zone is 
of special significance, for it gives much 
of the land marine climatic conditions. 




\ l 







"o -~ 



TO 

& . 



T3 : 
a " 

03 in 
— T3 

Wl.S 

.S £ 

o -a 



aS tJ 



ill 



fa 



156 ELEMENTS OF GEOGRAPHY 

Relatively small areas, in the widest parts of the continents, show 
true continental conditions. 



General Characteristics of Tropical Climates 

The most striking thing about the climate of tropical regions 
is its uniformity. The weather does not change frequently, as in 
middle latitudes. It is even said that the time of day may be told in 
some parts of the tropics from the pressure recorded by the barometer. 
The uniformity of atmospheric conditions day after day, and month 
after month, is so great that weather and climate are almost the same. 
Conclusions based on observations for a very few years, or even 
for a single season in some cases, are nearly as good as conclusions 
drawn from observations spread over many years. The regularity 
of weather conditions is occasionally interrupted by hurricanes and 
typhoons in rather restricted portions of the tropics (p. 138). 

Uniformity of Temperatures 

The average temperatures of the tropics are even more uniform 
than other elements of the climate. The lack of great variation 
depends on two facts: (1) the sun is always nearly overhead, and 
(2) the length of day and night is always nearly the same. As a 
result, the amount of insolation never varies much ; it is always large, 
and temperatures are both uniform and high. 

Annual changes. Many tropical localities show a range of 
less than io° between the mean temperatures of the warmest and 
coldest months, and a range of less than 15 is characteristic of most 
tropical lands (Fig. 93). On tropical oceans, and on some tropical 
lands, the range is insignificant. At Bogota, Colombia, the coldest 
month is less than 3 cooler than the warmest month. In any locality 
having a marine climate, the temperature of any one month is about 
the same as the temperature of any other month. Buitenzorg, on 
the island of Java, for example, has an annual range of only i.8°. 
Toward the edges of the tropical zone, the annual range of tempera- 
ture is greater, especially inland (Fig. 93). Thus at Nagpur, in the 
interior of India, Lat. 21 9', the range is 27.1 . 

Diurnal changes. In many parts of the tropical zone, the 
difference " in temperature between day and night is greater than 
that between the warmest and the coldest months. The daily range 
is greatest in dry regions far from coasts. In such places the tempera- 



TROPICAL CLIMATE 



iS7 



ture often ranges from a minimum of 50 
or 6o° at night, to a maximum of 120 in 
mid-afternoon. Since this is several times 
as great as the range between the warmest 
and coldest months, it is commonly said 
that "night is the winter of the tropics." 
The daily range is much the same day 
after day. 

At most tropical localities having ma- 
rine conditions, the temperature rarely 
falls below 70 , or rises above 90 . The 
temperatures of this zone are seldom be- 
low 55 , except at high altitudes, or above 
no° (Fig. 93). In some places, however, 
freezing temperatures have been known at 
sea-level, as in deserts near the margins of 
the zone. On the whole, however, the 
highest temperatures experienced in the 
tropics are no higher than those experi- 
enced every summer in middle latitudes. 
It is not so much the high temperature, 
as the continued high temperature, which 
distinguishes tropical climate. 

Effect of temperatures. The uni- 
formly high temperatures of tropical lati- 
tudes are significant in several ways: (1) 
Seasonal changes are so slight that they 
have little influence on life — animal or 
plant. The likeness of one day to another, 
and of one month to another, is probably 
a chief cause of the habit which tropical 
people have of putting off everything 
possible until "to-morrow." 

(2) In many tropical regions outside 
the deserts, the high temperatures are 
associated with high humidity. This 
means a high sensible temperature, which 
is uncomfortable and injurious in various 
ways. For instance, sunstrokes and heat 
prostrations are especially common among 



iJp? 



X? ; 






S d 



1) <u 



P^nTST 



i58 



ELEMENTS OF GEOGRAPHY 



V 



S =3 



b « 



2 -^ 
rf "S 



bO tn 



j 



<D 



-C >-, 



'3 o 



.2 ^ 



W rd 



C/3 o 

. 6 



white people. The dampness and heat are 
enervating. This effect is shown in the 
general laziness of tropical natives (p. 508), 
and the same trait appears sooner or later 
in most white people who remain there. 
The high temperature and humidity are 
also unhealthful, and together constitute 
one of the greatest obstacles to the life of 
white men in this zone. Diseases may be 
avoided, but in many places there is no 
relief from the "hothouse" air. 

One of the most important results of the high 
temperatures of tropical regions is that they per- 
mit vegetation to grow throughout the year, where 
rainfall is sufficient. Many trees bear buds, blos- 
soms, and ripe fruit at the same time. The bounty 
of nature seems unlimited. The effect of this con- 
dition on tropical natives is to increase habits of 
procrastination. 



Variability of Rainfall 
The variability of tropical rainfall is in 
contrast with the uniformity of the tern 
perature. The amount of rainfall varies 
greatly (Fig. 69), and so does its distribu- 
tion (Fig. 94). Some places are always 
dry, and others always rainy. In some 
places there is no rain for months at a 
time, and almost daily rains during the 
rest of the year. Some places have one 
rainy season a year, while others have two. 
This variability of rainfall is the control- 
ling factor in the climate where the other 
leading element, temperature, is nearly 
constant. In general, the variations of 
rainfall are definite and regular. 

Causes of variation. The amount and 
distribution of rain in the tropics are de- 
termined by the two factors, winds and 
topography. The winds (and calms) most 
important in determining the distribution 






TROPICAL CLIMATE 159 

of tropical rains are (1) the trade-winds; and (2) the equatorial calms , 
between the trade- wind zones. The calm belt moves north and 
south with the sun (p. 21), and its movements affect the extent and 
position of the trade- wind belts (Figs. 92 and 95). 

The periodic character of rains in much of the tropical zone 
depends mainly on the apparent migration of the sun north and 
south of the equator. For most localities within the limits of the 
migrating belt of calms, the rain comes when the sun is nearly over- 
head. This type of rainfall might be described as summer rain, though 
the period of its occurrence is marked, in some places, by tempera- 
tures lower than those prevailing at other times. Topography (alti- 
tude), especially within the trade- wind zones, is an important factor, 
for rain is likely to fall from air forced up over high elevations 
(p. 122). The distribution of land and water also determines, to 
some extent, the relation of winds to rainfall. 

Seasons of rainfall. The monthly distribution of rainfall gives 
a basis for the division of the year into seasons. This division is two- 
fold for parts of the zone, and fourfold for other parts. Thus some 
places have two seasons, one rainy and one dry, while others have 
four seasons, two rainy and two dry. No general statement can be 
made as to the length of these seasons. Some places with only two 
seasons have a dry season of eight months and a rainy season of four, 
while in others these relations are reversed. Hence, the lengths of 
the seasons in the tropics vary from place to place. Rainfall is here 
chief among the factors which control the distribution of life, and 
many of its relations. This is illustrated (1) by the rapidity with 
which vegetation springs up when rain begins after a long dry season; 
(2) by the fact that over millions of square miles the planting of 
crops depends on the coming of rain; and (3) by the fact that even the 
nesting of many birds takes place only in the rainy season. 

Types of Climate within the Tropics 

Rainfall and its effects furnish a basis on which different types of 
tropical climate may be distinguished. There are four principal 
types: (1) The equatorial type, affecting a zone of io° to 15 on either 
side of the equator (Fig. 94) ; (2) the trade-wind type, affecting belts 
outside the equatorial zone; (3) the monsoon type; and (4) the 
modifications due to altitude, giving what may be called mountain 
climate. 



i6o 



ELEMENTS OF GEOGRAPHY 



? 



sjti_ 






Equatorial Climates 

Temperature. Temperature is least 
variable in the equatorial part of the trop- 
ical zone (Fig. 93). Within the equatorial 
belt, the differences of temperature depend 
chiefly on (1) nearness to the sea, especially 
nearness to that sea from which the wind 
blows to the land, and (2) altitude. The 
typical marine climate of this belt has 
practically no change of temperature from 
month to month. Thus Batavia, the cap- 
ital of Java, has a mean annual temper- 
ature of, 7 8. 8° F., and a yearly range Of 
only 2 . The greatest changes of temper- 
ature occur in continental interiors and 
on high plateaus. Thus in the interior of 
central Africa (Fig. 93), the mean annual 
temperature may be the same as that at 
Batavia, but with a range of io° or 12 
from 'the warmest to the coldest month. 

The daily range of temperature near 
the equator is almost always greater than 
the annual range. Quito, Ecuador, Lat. 
o° 14' S., at an altitude of 9,350 feet, has 
an annual range of less than i°; but 
throughout the year the temperature in 
early morning is about 47 , while at mid- 
day it is about 66°. On coasts and islands 
in similar latitudes, the daily range is much 
less, say from 90 to 75 . People living 
under the latter conditions are very sensi- 
tive to marked changes of temperature, 
and for them a temperature below 70 
may mean actual suffering. In the equa- 
torial belt, frost on low lands near the 
sea is unknown. Hence, the development 
of vegetation is greater here than else- 
where, if other conditions are favorable 
(Fig. 96). 



TROPICAL CLIMATE 161 

Rainfall. The rains of the equatorial belt come, for the most 
part, in daily showers, and, contrary to common opinion, long- 
continued rains are rare. During even the season of greatest 
rain, almost every day has a clear morning, and the rain comes 
from thunder-storms in the afternoon. These thunder-storms re- 
sult from convection currents in the belt of equatorial calms. 
In many localities they come with marked regularity at a cer- 
tain hour in the afternoon, — so regularly, in fact, that in some 
places social engagements are made to be kept "after the shower 
is over." 

Subdivisions of equatorial climates. The migration of the 
belt of calms (Fig. 95) involves the movement of the zone of daily 
thunder-storm rains. This calm belt varies, both in width and 
amount of migration. In general, it is widest over the lands, 8°-i5° 
of latitude, and narrowest over the oceans, 2°-io°. Its migration 
usually amounts to io° or more on land. All places affected by the 
belt of calms have wet and dry seasons. Two general types of 
equatorial climate are recognized. The first, known as the true 
equatorial climate, has two rainy seasons and two dry ones, and affects 
a zone about io° wide on each side of the equator. The other, com- 
monly known as the tropical climate, has one rainy season and one 
dry season, and affects narrow zones beyond latitudes io° N. and io° 
S. In the area having the true equatorial climate, rain is plentiful 
(Fig. 69) . The dry seasons are short, and in most cases not altogether 
rainless (See Table I below). The tropical climate has a short 
rainy season of three to five months, and a long dry season of seven 
to nine months (Table II below). Dry seasons of this type may be 
almost rainless. 

The lengths of the seasons and the dates of rain and drought 
depend on the movement of the belt of equatorial calms. The migra- 
tion of this belt follows the vertical position of the sun, but lags 
somewhat behind. Thus, at the equator the rainfall does not reach 
its maximum at the time of the equinoxes, but a month or more 
later (April and May, and October and November). Between the 
two periods of greatest rainfall, there is a time when rain is scanty, 
or during which, in rare cases, none falls. Bogota, Colombia, shows 
the typical monthly distribution of equatorial rainfall. This type of 
rainfall is fairly reliable, for there is little variation in the time of 
its coming, from one year to another, and the amount which falls is 
commonly adequate for all needs. 




162 ELEMENTS OF GEOGRAPHY 



Table I 
Equatorial Type of Rainfall (Monthly average in inches) 1 
Bogota, Colombia. Latitude 4 35' N. Altitude 8,727 feet. 

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year 2 
2.7 3-5 4-9 9- 6 6 -5 3- 1 2.6 3-3 2.9 8.4 9.5 5.6 64 

Equatorial Type of Temperature , 
Mean Annual Coldest Month Warmest Month Mean Max. Mean Min. 
57.9 56.8° (July) 5 8. 6° (March or April) 71.9 45. 8° 

The rainfall of the tropical climate, as distinguished from the 
equatorial, is illustrated by Cochabamba, Bolivia, which has a nearly 
rainless season from April to November. As a rule, the farther places 
with tropical climate are from the equator, the shorter their rainy 
season. 

Table II 
Tropical Type of Rainfall (Monthly averages in inches) 1 

Cochabamba, Bolivia. Latitude 17 20' S. Altitude 8,400 feet. 
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year 2 
4.2 3.5 2.4 0.4 0.4 0.27 0.19 0.15 0.66 0.59 1.2 3.9 18. 1 



-2 



Tropical Type of Temperature 

Mean Annual Coldest Month Warmest Month Mean Max. Mean Min, 

6i.S° 55° (June) 66.5 (Oct. or Nov.) 86.3 27.1° 

North of the equator, the rainy season of the tropical climate 
begins in May or June, and continues until September or October. 
South of the equator (as Cochabamba), the rainy season begins about 
November and lasts until March. Since there is no great difference 
in temperature between the various months of the year, the value of 
rainfall for crops is about as great at one time as another. On the 
whole, the tropical rainfall is (1) less and (2) more variable (a) in 
amount, (b) in time of coming, and (c) in duration, than equatorial 
rainfall. 

Humidity and cloudiness. In the equatorial climate, the humid- 
ity is relatively high much of the time. In the tropical climate, the 
humidity is low during the dry season, and high while the rains last. 
While high humidity has ill effects on tropical people, as already 

x Data adapted from Hann, Handbuch der Klimatologie, Vol. II. 

2 Total for year includes odd hundredths of inches omitted from monthly figures. 



TROPICAL CLIMATE 



163 



pointed out, it is advantageous locally, for 
it is an important factor in the formation of 
heavy dews. Thus, it is said that in some 
tropical forests the dew is equivalent to a 
light shower. This is of great benefit where 
the rainfall is scanty. Cloudiness is rather 
common, especially where the equatorial type 
of climate is found. The clouds are formed 
in the strong convection currents of the belt 
of calms. Where there are two rainy seasons, 
there may be cloudiness 70 or 80 per cent of the 
time. Where there is but one rainy season, 
as in localities farther from the equator, the 
long dry season is accompanied by little cloud- 
iness. Tropical climates, as distinct from 
equatorial climates, are prevailingly sunny. 

The distribution of rain and clouds 
throughout the year affects the tempera- 
tures of the different months. As a rule, the 
end of the dry season has the highest tem- 
perature (Cochabamba, Oct. -Nov.), and the 
rainy season is, in many places, the coolest 
part of the year, though the sun is then 
highest. This is due to the fact that the 
clouds shut off the sun's rays for a consider- 
able part of the day. The increased humid- 
ity of the less hot rainy season makes its 
sensible temperature higher than that of the 
hotter dry season. In many places, there- 
fore, the rainy season is the most disagree- 
able time of year. Some tropical diseases 
are also most prevalent then. 

Equatorial climate and life. Because 
of the climate, the soil of tropical regions is, 
on the whole, poorer than that of middle 
latitudes. The high temperatures favor the 
thorough decomposition of the rocks to form 
soil, but the heavy daily rainfall, during 
much of the year, leaches from the soil many 
of its more soluble and valuable elements. 



^ <$< 



„ M <J W U. 

nil 



Pn 



I! 



i6 4 ELEMENTS OF GEOGRAPHY 

The high temperature and abundant rainfall, however, give the condition 
necessary for a luxuriant growth of vegetation, even on inferior soils, and thi 
growth favors the development of humus, which tends to improve the soil 
Dense forests, such as those in the Amazon Valley, in central Africa, in the Malaj 
Peninsula, and on the neighboring islands, are characteristic of the equatoria 
climate (Fig. 96). 

These equatorial forests are inhabited only by relatively sparse population; 
of backward natives, who live chiefly by hunting and fishing, and by using th< 
abundance of food supplied by the forest (p. 509). Since the rainy season causes 
floods in the low lands, and drives away many of the animals upon which the 
natives depend for food, some of the native religious ceremonies contain prayer 
for a long dry season. The density of the forest makes travel and communicatior 
easy only by way of rivers. 

The true equatorial climate is unhealthful, especially for white 
people. Tropical malaria, yellow fever, and intestinal disorders, 
like dysentery, are the worst enemies which the white man meets 
near the equator. All these reach their maximum during the rainy 
season. The first two are .spread by mosquitoes, and consequently 
are associated with swampy places. 

Along the Amazon Valley, and especially on the equatorial coast of Africa, 
fevers practically control the location of residences for white settlers. If the 
white man escapes these diseases, there is still the climate itself with which he must 
contend. The never-varying high temperature, and the excessive moisture, month 
after month, with never any stimulus from invigorating cold, gradually have 
their effect. The damp, hot air reduces evaporation from the body, and dilution 
of the blood results. The characteristic tropical anaemia appears sooner or later 
in most cases, and unless he seeks recuperation in a colder climate, the white man 
loses his physical and mental vigor. 

Effect on transportation and trade. It is necessary to emploj 
a force of men simply to keep the tracks of some tropical railroac 
clear of vegetation. Many of the wagon roads which are buil 
become impassable in the rainy season. In some regions a muc 
sledge, hauled by a water buffalo, is used in the wet season, but 
it is a very primitive and unsatisfactory mode of conveyance. 

During the rainy season the rivers are swollen, and travel by boat is easier 
than at other times, for great sections of country are then flooded. Thus the 
southern tributaries of the Amazon overflow their banks almost every year, and 
cover an area as large as the state of Pennsylvania with several feet of water. 
Habitations are moved to the higher points, but movement from one place to 
another goes on with ease. 

Wooden railroad ties and telegraph poles decay rapidly, and it is necessary, 
in constructing railroads in parts of the tropics, to use special woods, like camphor 



TROPICAL CLIMATE 165 

and lignum vitae, or to substitute iron and concrete. The effect of all these things 
is to retard commerce. The most favored localities for trade in equatorial regions 
are those where a large river offers a natural trade route, and the river port is, 
therefore, the commercial center. Para and Manaos, on the Amazon, are examples 
of cities developed by river traffic through an equatorial forest. The commodities 
handled are largely forest products (p. 512). 

Tropical climate and life. Where this type of climate pre- 
vails, the general absence of rainfall through the larger part of the 
[year leads to vegetation very different from that found nearer the 
equator. Grass lands replace dense forests (Fig. 96). The llanos of 
Venezuela, the campos of Brazil, and the Sudan in Africa are the 
-.best examples of this type. In general, these regions are without 
forests, since the short period of growth, limited chiefly to the rainy 
season, is not sufficient for trees. Scattered patches of forest, how- 
Lever, are found here and there, as in the campos of Brazil. 

The people of the grass lands are more advanced than the forest- 
dwellers of equatorial lands. They derive much of their support 
from flocks and herds. The necessity of moving frequently to find 
new supplies of forage for the cattle, goats, or camels, makes many 
of these pastoral people nomadic. 

In favored localities, however, they become permanent settlers, cultivating 
the soil. Such localities are, in most cases, where irrigation is possible. Outside 
the irrigated lands, crops are planted in the rainy season only, and only in places 
where the rainfall is considerable. The latter varies from year to year, and some- 
times fails to come at the expected time. This has retarded the development 
of agriculture, and has led to frequent famines, even among people dependent on 
their flocks, for the want of new vegetation when the rains fail causes the animals 
to die of starvation, by hundreds and thousands. 

Irrigation, however, may yet make much undeveloped tropical 
land productive, and on such land, white men may live with more 
comfort than nearer the equator. The low humidity through much 
of the year makes the high temperature easier to bear. It means 
also a greater daily range of temperature, with cooler nights which 
afford relief from the heat. The tropical type of climate is also more 
healthful than the equatorial. For all these reasons, the open grassy 
plains are more suitable for white men. The llanos of Venezuela, 
the campos of Brazil, and the African Sudan are, therefore, important 
parts of the tropics, with respect to future development. 



i 



166 ELEMENTS OF GEOGRAPHY 

Trade-Wind Climate 

Winds and temperature. The most striking feature of the 
trade-wind climate is the steadiness of the winds, which blow with 
a velocity of 10 to 30 miles an hour throughout the year. On the 
whole, the velocity is somewhat higher in the southern hemisphere, 
because the larger extent of water surface there means less friction 
of the moving air. One effect of this steadiness of wind is to make 
the temperature conditions simple, especially over the oceans, and: 
the climate of islands which lie in the trade-wind zone is about the 
simplest in the world. 

In spite of the simplicity of climatic conditions in the trade-wind 
zones, both annual and diurnal changes of temperature are greater 
" than in the equatorial belt. Low lands swept by the trades tend to 
be arid. They are warmed rapidly by day, and cooled rapidly at 
night, having in many places a diurnal range of 50 or 6o°. Tempera- 
tures as low as 32 are known. These great changes are felt less than 
equal changes in the equatorial regions would be, because the humidity 
is low. The drier air, with its greater changes of temperature, makes 
the arid and desert lands more healthful than most equatorial regions. 
The desert climate may be described as almost invigorating, and 
common tropical diseases practically are absent. The trade-wind 
zones, therefore, do not present the same kinds of difficulties to 
human habitation as the equatorial regions. The variations of 
temperature over the ocean, and near it, are less than in the interiors 
of continents (Fig. 93). ' 

Rainfall. Though commonly drying winds, the trades contai 
much water vapor, and become wet winds when cooled to the devs 
point. They are not so cooled over the lowlands, hence the latter 
are dry as long as the trades blow. Where they blow throughout the 
year, a desert is the result (Fig. 69). On the other hand, wherever the 
trades blow over highlands, the ascending air is cooled, and clouds 
may form and rain fall. For this reason, the windward sides of 
highlands in the trade-wind belts are likely to be rainy, while 
the leeward sides are generally dry (Fig. 69). Thus the leeward 
(westward) side of the Andes, from Ecuador to northern Chile, 
presents the strange spectacle of a coastal desert, and a similar 
condition is found on the leeward coast of southwest Africa. High- 
lands standing in mid-ocean also have a rainy side toward the 
trades, and a drier side in the lee, as illustrated by the Hawaiian 






TROPICAL CLIMATE 



167 




Fig. 97. 



islands. Where two islands are separated by a narrow strait, the 
windward side of one may receive rain every day, while the leeward 
side of the other, across the 
strait, is parched and dry. 

In Australia (Fig. 97), a con- 
tinuous highland lies close to the 
east coast, directly across the 
path of the southeast trades. 
The effect of this barrier is to 
increase the area of the inte- 
rior desert, sometimes called the 
"dead heart of Australia," and 
greatly to restrict the spread of 
population (Fig. 98). The im- 
portance of high lands in getting 
rain from trade-winds is seen in 
the fact that even in deserts, as 
on the Macdonnell ranges in cen- 
tral Australia, and on local ele- 
vations in the Sahara, rain falls 
and vegetation flourishes (p. 504). 
Streams flow for short distances 
from the mountains, but soon 
dry up or are absorbed into the 
sands of the desert below. 



Most low lands affected 
iby the trades are, on the 
whole, sunny; trade- wind 
deserts are almost cloud- 
less. This fact may have 
significance in the future, 
in the possible generation 
iand storage of power de- 
rived from the heat of the 
sun's rays. Cloudiness is 
confined chiefly to wind- 
ward slopes, which repre- 
I ;sent, on the whole, but a small part of the total area of the trade- 
wind zones. 

The time of the rainy season in the trade-wind belts varies from 
one locality to another. In some places the rainfall is distributed more 
or less evenly throughout the year, as at Hilo, in the Hawaiian Islands 
(Table III). In other places it is seasonal, as at Hue, the capital of 




Fig. 98. 

Fig. 97. Mean annual rainfall for Aus- 
tralia. (Diercke.) 

Fig. 98. Map showing density of popu- 
lation per square mile in Australia. (Lyde.) 






168 ELEMENTS OF GEOGRAPHY 

Annam (Table III). This variation depends largely on the steadiness 
of the wind. Places so situated as to get rain from the trade-winds 
have no rainless season if the winds are fairly steady throughout the 
year, as in the central parts of the trade-wind zones. Such places 
usually tend to have more rain when the sun's altitude is lowest, that 
is, in the winter months. In other places, however, as along the east 
coast of South America south of the equator, the winter trades are 
interfered with by cold air moving outward from the interior high- 
lands, and the maximum rainfall comes in summer (Sao Paulo, 
Table III). Table III shows three different types of trade- wind 
rainfall. 

Table III 
Trade-Wind Rainfall — Windward Coasts. 1 (Monthly averages in inches.) 

Lat. Jan. Feb. Mar. Apr. May June 

Hue, Annam i6° 33' N. 4.9 4.3 2.3 1.9 2.2 1.8 

Hilo, Hawaii i9°4o'N. 12.7 16.7 n. 3 12.0 8.6 7.6 

Sao Paulo, Brazil 23 33' S. 10.6 8.4 5.5 3.1 3.2 2.5 

July Aug. Sept. Oct. Nov. Dec. Year 

Hue, Annam 2.6 5.0 18. 1 26.1 24.1 8.2 102 

Hilo, Hawaii 11.0 11.3 11.3 15.0 11. 6 16.2 145.2 

Sao Paulo, Brazil 1.0 1.6 3.2 4.4 4.0 6.3 54.1 

Any of these types of trade-wind rain may be complicated by the 
tropical type, if the station concerned is in a latitude low enough 
to be reached by the equatorial calms. A locality affected alternately 
by the trade-wind and the tropical types of rainfall is likely to have 
two seasons of heavy precipitation — one (tropical) about the tir 
the sun is overhead, the other (trade-wind) about the time the sur 
is lowest in the sky, — with short, less rainy seasons between. 

Trade-winds are interrupted in some places by winds due to 
seasonal differences of temperature over large land areas (p. 115) 
When this is the case, a third type of rainfall, the "monsoon" type 
occurs in the trade-wind zone. The monsoon rain comes when the 
sun's altitude is greatest, and when the monsoon winds, displacing 
the trades, blow to high lands. Hence, it is a summer rain. It cor 
monly occurs in latitudes higher than those where the equatorial type 
of rainfall is found. 

Cyclones of the trade-wind belt. The normal weather condi- 
tions of trade-wind belts are interrupted by tropical cyclones. They 

*Data from Hann, Vol. II, pp. 217 (Hue), 268 (Hilo), and 351 (Sao Paulo). 



TROPICAL CLIMATE 169 

appear to originate over islands along the margins of the equatorial 
belt, and move to higher latitudes through the trade-wind zone 
(Figs. 82 and 86). These storms are confined almost wholly to the 
season when the equatorial calms are farthest from the equator. 
The migration of this belt is both slower and less over the oceans than 
over the lands. Hence these storms occur only during a few months, 
usually late summer and early autumn, and at opposite times of the 
year on the two sides of the equator. They interrupt the regular 
daily changes of temperature, and in many cases give torrential rains. 

The particular importance of the tropical cyclone is in connection with the 
destruction of life and property by wind and flood. The loosely built native 
houses offer little resistance to the violent winds. Crops are beaten down by 
wind and rain, and in many cases the destruction is nearly complete. 

Relation of trade-winds to commerce. The steady, reliable 
trade-winds which prevail over a wide, east-west belt of the oceans 
have long been an important factor in determining the courses of 
sailing vessels. 

Most sailing routes crossing the equator have been influenced by the trade- 
winds, and the routes for out-bound and in-bound vessels are different. Thus 
whaling vessels out-bound to the Pacific from New Bedford (Mass.) commonly 
crossed the Atlantic to the Cape Verde or Canary Islands before turning south. 
This practice led frequently to the employment of Portuguese sailors from those 
islands, and the introduction of a Portuguese population into some of the New 
England whaling ports. Vessels in-bound from the Pacific usually swing around 
Cape Horn, far out into the South Atlantic (Why?), and thence sail directly 
home. Sailing routes are unlike steamer routes, for steamers generally follow 
about the same course in both directions. The Panama Canal will probably be of 
little importance to sailing vessels going east, on account of adverse winds. 
Similarly, the Red Sea presents head winds to a sailing vessel attempting to pass 
from the Indian Ocean to the Mediterranean. 

Trade- wind climate and life. Temperature conditions are 
almost as favorable for vegetation in the trade-wind zone as in the 
equatorial belt, but moisture is scanty. Forests as dense as those of 
the equatorial belt are common on rainy windward coasts or high- 
lands, but most of the lands of this zone ar^ arid (Fig. 96). The 
Sahara and the desert of Australia are each more than two-thirds the 
size of the United States. Trade-wind deserts have little vegetation, 
and, except in oases, no plants of value (p. 499). 

Considering the tropical zone as a whole, vegetation decreases in 
amount from the equator out (Fig. 96). This is illustrated strikingly 
in Africa, where a broad land area extends beyond the tropics both 



1 



170 ELEMENTS OF GEOGRAPHY 

north and south of the equator. Near the equator, there is the 
dense equatorial forest, and on either side of it lie belts of grassy vege- 
tation which are developed best at the north, in the Sudan. North 
of the Sudan is the Sahara, with little or no vegetation. The few 
plants of the desert are such as can withstand the dryness (p. 499). 
Vegetation is so scanty that the people, depending for support mainly 
on a few animals, have to move frequently from one source of water 
to another. Native animals show adaptations to their surroundings 
in respect to color, speed, means of self -protection, and other matters 
(p. 500). South of the equator, in the area corresponding to the 
Sahara, the continent is narrow and the land high, so that desert 
conditions are not fully developed. 

Deserts interfere in many ways with travel and communication 
among men, and a desert 'is almost as effective as the ocean in pre- 
senting a barrier to the spread of plant and animal species (p. 500). 
Since most beasts of burden cannot stand desert conditions, caravan 
trade is carried on chiefly with the help of camels (p. 501). 

Railroad building across deserts is interfered with in various ways. Wooden 
ties literally dry up and blow away; blowing sand is likely to cover the tracks; 
fuel and water are scarce or lacking; and cars must be of special construction to 
withstand the dryness of the air. Hence problems of travel and communication 
are difficult, and not one of the many projects for railroads across the great deserts 
of Africa and Australia has been completed. Such roads would be of great value, 
because they would connect fertile lands on opposite sides of the desert. 

Human life in the desert is influenced greatly by the climate 
(p. 501). Food and useful materials of all kinds are scarce, yet the 
greater changes of temperature necessitate more clothing than is 
needed in the equatorial belt. White clothing is worn commonly, 
because it absorbs less sun-heat than dark fabrics. The clothing is 
loose, partly because such clothing is more comfortable in the heat, 
■ and partly because the danger of dust-storms makes it desirable 
to have a covering which can be drawn over the head. The 
people of deserts usually live in tents, or in loosely constructed, low, 
flat-roofed houses. There is no need for shutting out cold or rain. 
Where solidly built, the flat-roof makes a good place to sleep. 

Since ordinary fuel is commonly scarce or absent in the desert, 
the only source of artificial heat, in many places, is the dried dung 
of animals like the camel. With such a scanty supply of fuel, 
cooking is of the most primitive sort. This fact leads, in part, to a 
general diet of curds, milk, etc. Where meat is used, it is often air- 



TROPICAL CLIMATE 171 

dried, a process made possible by the low humidity. Utensils, like 
vessels for holding water, are made of leather — about the only 
serviceable material available in many places. 

The use of water for bathing is unknown in many desert localities, 
because of the scant supply. Even where water is to be had, some of 
the natives claim that its use makes the body more sensitive to tem- 
perature changes. The sand-bath is common. 

In parts of the deserts, showers occur now and then. In some 
places they come regularly at certain seasons of the year, and, in 
favored spots, the rainfall is enough to grow grain. In the latter 
case, the rainfall has a marked effect on the customs and religions of 
the people. In some places, elaborate ceremonies are performed in 
honor of the rain gods, before the seeds are planted. It is interesting 
to note, however, that the time for these ceremonies usually is deter- 
mined by the cleverer persons, who know, better than others, when 
rains may be expected. In some desert regions, therefore, the wor- 
ship of rain, of rain clouds, or of the gods supposed to control them, 
is common. Sun worship is also common in most religions of desert 
people, as in that of ancient Egypt; for the sun is one of the most 
prominent things of the desert. Desert conditions, therefore, affect 
man in many different ways (pp. 501-506). 

Monsoon Climate 

Rainfall. In some countries, at the season when the sun's alti- 
tude is greatest there, the trade-winds are overcome by the tropical 
monsoon. While the monsoon lasts, it blows in many places with 
the steadiness of the trades. Since this wind owes its origin largely 
to a favorable distribution of land and water (p. 115), it is not found 
everywhere in the trade-wind belts. 

Monsoons are well developed in southern and southeastern Asia, especially 
in India and thence to the China Sea. On the eastern coast of Asia, northward 
nearly to latitude 50 , there is a somewhat similar oceanic wind in summer, which 
gives some rain to the land. The time of the tropical monsoon is fairly definite 
because of its relation to the altitude of the sun. For most places in the northern 
hemisphere, the monsoon season is between May and October. In the southern 
hemisphere, especially northern Australia, it is from November to April. The 
monsoon wind generally brings rain. Over lowlands, the rain results from the 
strong convection above the hot land to which the wind blows; on the windward 
sides of high mountains, the rain is much heavier, a fall of 400 to 500 inches a year 
occurring in some places. Since it all falls in five to six months, this means a 
daily rainfall of two to four inches throughout the rainy season. 



172 ELEMENTS OF GEOGRAPHY 

The conditions which produce rain mean increased cloudiness, 
and so the rainy season may be less hot than the others. As a rule, 
the highest temperatures occur just before the rainy season begins 
(Bombay, Table IV), for at this time the regular winds become weak 
or fail altogether. During the rainy season, the increased humidity 
more than offsets the comfort which the slightly lower temperatures 
might afford. 

The Indian monsoon is a southwest wind (Fig. 66), blowing from 
the Indian Ocean and the Bay of Bengal. Western and southwestern 
slopes therefore receive much rain, but the eastern coast, in the lee 
of the Deccan plateau and Eastern Ghats, gets little rain while the 
monsoon blows (Fig. 94). .This coast gets its rain when the north- 
east trade-wind blows. In northwestern India there is a large desert, 
not reached by the monsoon. Hence different parts of India have 
different types of rainfall, largely as a result of the relation of wind 
direction to topography. The larger part of the country, outside 
the desert, however, has a rainy season from May to October, and 
a dry season during the rest of the year. This is illustrated by the 
monthly rainfall averages for Bombay: 

Table IV 

Monsoon Type of Rainfall l (Monthly averages in inches) 

Bombay, India — Latitude 18 54'. 

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year 

0.1 000 0.5 20.78 24.68 15. 1 10.78 i.8 0.5 0.07 74.4 

Temperature, at Bombay 2 

Mean Annual Coldest Month Warmest Month Mean Max. Mean Min. 

79.5° 73° (Jan.) 84.7° (May) 95° 6i° 

During the dry season, many localities are practically rainless. 
This season also is sunny, and where the trade-wind is felt distinctly, 
it may be cool and agreeable. In many places, however, the dry 
season is hot and disagreeable. 

There are no important monsoon districts in the tropical lands of 
the western hemisphere, because there the arrangement of land and 
water areas is not favorable for their development. Besides southern 
Asia, northern Australia (Fig. 97) and the northern coast of the Gulf 
of Guinea (West Africa) have distinct tropical monsoon climates. 

*Data from Hann, Vol. II, p. i8<x 
2 Data from Hann, Vol. II, p. 174. 



TROPICAL CLIMATE 173 

Importance of monsoon rains to people. The importance of 
the monsoon rainfall to southern Asia can hardly be over-emphasized. 
During the dry season all vegetation withers, and the earth is parched 
and dusty. Hence the growing of crops, and the support of the 
people over vast areas, depend on the regular appearance of the rain- 
producing monsoon. 

For one reason or another, these southwesterly winds sometimes fail, and still 
pftener they do not appear when they should. At still other times, they stop 
sooner than usual, and finally, they are sometimes interrupted during what should 
be their proper season. The failure of the rain means loss of crops and famine 
for the dense populations of the monsoon districts. Famines usually leave hundreds 
of thousands of people in a weakened condition, so that ravages of epidemic 
diseases, like bubonic plague and Asiatic cholera, commonly follow a famine. 
In India, deaths from famine and disease have exceeded a million in many differ- 
ent years. So great has been the loss of life, in some cases, that laborers enough 
to cultivate the farms were not left. The famine districts are not in the 
irrigated localities, or in the desert sections of northwestern India, but in the 
regions of moderate rainfall (30 to 50 inches), where, in normal years, there is 
water enough for the crops. In other places, especially in southern China, too 
much rain sometimes produces disastrous results. Rivers rise high above their 
banks, destroying much property and many lives; and famines, resulting from the 
destruction of crops, at times cripple whole provinces. Riots in some of the 
cities of southern China in late years have been traced directly to floods and 
famines. 

Monsoon countries as a whole are populated densely, containing 
the larger part of the population of the tropical zone. They offer 
rather easy conditions of life, so far as the requirements of man are 
concerned, and the soils generally are productive when rains are 
regular. The crowding of people in monsoon districts is indicated 
by the fact that 300,000,000 people live in India, in an area less than 
two-thirds that of the United States. 

Altitude as a Climatic Control in Tropical Regions 
Effect on temperature. For most of the tropical zone, vary- 
ing altitude is the one factor which causes important variations in 
temperature. The extent of this variation is suggested by the fact 
that tropical mountains exceeding 16,000 feet are snow-capped. 
Thus the volcano Cayambe, which stands directly on the equator in 
Ecuador, has permanent glaciers near its summit, at an altitude of 
about 20,000 feet. 

The lower temperatures found at moderate altitudes make pla- 
teaus in the tropics more agreeable and healthful than lowlands. 



174 



ELEMENTS OF GEOGRAPHY 



White people living in the tropics seek the highlands, whenev 
possible, for residence (p. 486). On the Bolivian plateau, for example, 




Fig. 99. Map showing density of population per square mile in South Amer- 
ica. (Lyde.) 

the daily temperature may range from a minimum of 32 , to a maxi- 
mum of 75 or 8o°. 






TROPICAL CLIMATE 175 

The effect of the lesser heat even at altitudes of 7,000-8,000 feet 
is not, however, equal to an invigorating cold season, like the winter 
of middle latitudes. The climate of tropical mountains and plateaus 
is somewhat like the marine climate of the temperate zones. Both 
are sometimes spoken of as being like "perpetual spring." 

Vegetation affected by altitude. The vegetation, native and 
cultivated, of the higher altitudes of the tropical zone resembles 
that at lower levels outside the tropics. For example, on tropical 
highlands in Bolivia wheat and potatoes are common crops, whereas 
on most tropical lowlands they cannot be grown at all, or not as 
profitably as rice. There is a gradual change with increase of alti- 
tude, from products like sugar-cane or rice in the lowlands, through a 
belt of temperate-zone fruits or vegetables at a moderate altitude, to 
cold-temperate and arctic types of plants, and then to perpetual 
snow at an elevation of about 16,000 feet. The snow and ice- on the 
heights help to supply water for irrigation below. In places, too, the 
ice of the high mountains is carried down to settlements below. 

Population affected by altitude. The most important effect of 
the highland temperatures is seen in the distribution of the popula- 
tion. From Mexico to Bolivia, most of the highlands are well popu- 
lated, and the lowlands sparsely (Fig. 99). The single exception is in 
Peru, where three-fourths of the people live on the coastal lowland, 
which is dry and healthful. The effect of altitude appears also in 
the location of the cities, many of which are found at elevations 
exceeding 5,000 feet, and some of them are above 10,000 fee.t, as 
shown below. 

Tropical American Cities at High Altitudes 

Mean Temperature 

Warmest Coldest 

City Latitude Altitude Population Month Month 

Caracas io° N. 4,000 90,000 73-9° 68. 5 

Guatemala 14° N. 4,850 125,000 68.5° 62. o° 

Mexico City 19 N. 7, 350 350,000 64. 5 53-6° 

Bogota 4° N. 8,630 120,000 58. 6° 56. 8° 

Quito o° 9,350 80,000 56. 6° 56. i° 

La Paz 16 S. 12,200 70,000 54-5° 45-! 

The temperatures of cities in middle latitudes are in strong contrast with the 
above : 

Philadelphia Lat. 39° 56' N.; warmest month, 75. 9 ; coldest month, 31. 2° 

St. Louis Lat. 38 37' N.; warmest month, 78. o°; coldest month, 31. i° 



176 ELEMENTS OF GEOGRAPHY 

In tropical America, it is common for the chief city to be on the 
highland in the interior, and for a smaller city, serving as a commer- 
cial outlet, to be on the hot, damp, and unhealthful plain close to the 
sea. Mexico City and Vera Cruz; Caracas and La Guayra; Sao Paulo 
and Santos, are examples of such pairing. Outside the cities, the 
highlands are the most thickly settled and the best developed sec- 
tions, while the lowlands have few people, chiefly natives, and are 
but little developed. The result is that many of the chief products 
of tropical lands are not truly tropical in character. 

The decreased pressure of air which goes with increased altitude 
is of some importance in the higher tropical lands. It is generally 
true that the natives living at high altitudes (in Bolivia up to 15,000 
feet) have a large lung capacity, on account of the rarefied condition 
of the atmosphere. These natives are active and well under their 
natural conditions, but usually sicken if taken to low altitudes. Con- 
versely, natives of lowlands often experience much discomfort at 
high elevations. The difficulty of keeping native laborers at altitudes 
of 4,000 to 5,000 feet is said to have retarded the cultivation of coffee 
in Brazil. In most localities, however, the ill effects of lessened pres- 
sure are not felt below 5,000 feet. Hence diminished pressure is 
not likely to affect seriously the growth of population in tropical 
highlands. 

The Future of the Tropics 

Because of their more comfortable temperature and more health- 
ful conditions, the highlands of the tropics will probably be highly 
developed earlier than the lowlands. At altitudes above 2,000 or 
3,000 feet, tropical diseases, particularly malaria and yellow fever, 
are not prevalent. Civilized peoples can live comfortably at these 
altitudes, and where they have not already done so, they are likely 
to establish themselves in lands of moderate height where there is 
adequate water, and from them direct the development of the 
adjoining lowlands, the products and resources of which are of so 
much importance to the commercial world. 

Questions 

1. What sort of climate would prevail where the Gulf of Mexico and the 
Caribbean Sea are, if those areas were land? 

2. What effect would such a land area have on the climate of northern South 
America and Central America? 

3. In what respects would weather forecasting in Brazil differ from weather 
forecasting in the United States? 



TROPICAL CLIMATE 177 

4. Why do annual temperature ranges increase toward the margins of the 
tropics? Why are the highest temperatures not found along the equator? 

5. Why is it advisable for white men in the tropics to wear clothing of 
different weights in midday and evening? 

6. Explain the necessary relation of a place to the equatorial belt of calms, 
in order that it may have two distinct rainy seasons and two distinct dry seasons. 

7. Classify the different sections of tropical America under the types of climate 
given on page 161. 

8. Why is there no desert in that part of tropical South America east of the 
Andes? 

9. Suggest ways in which tropical climates might affect the character of 
imports from the outside world. 

10. What changes would be produced in the climate of Australia if the main 
mountain range stood along the west coast instead of along the east coast? 

n. Which of the two important tributaries of the Nile is the first to be in 
flood each year? Why? Which has the greater flood? 

12. Suggest reasons which might delay the arrival of the Indian monsoon. 

13. What relation does the warmest month at Cochabamba bear to the summer 
solstice for the southern hemisphere (p. 162)? How does this compare with condi- 
tions in the latitude of Chicago? Explain the difference. 

14. Explain the distribution of rainfall in Australia (Fig. 97). 

15. What industries are likely to be connected with the distribution of popula- 
tion and rainfall shown in Figs. 97 and 98? 

16. Explain the course of the line showing the poleward limit of palms in 
Fig. 92- 

17. Why do some areas in the tropics (Fig. 94) have more rainfall in the winter 
than in the summer half-year? 

18. What reasons account for the scanty population in the interior of Brazil 
(Fig. 99)? Compare Fig. 99 with Figs. 69, 93, and 96. 



References 

Dastre: The Fight Against Yellow Fever, in Smithsonian Ann. Rept., 1905, 

Part I, pp. 339-350. 

Ford: Tropical America. (New York, 1893.) 

Giles: Climate and Health in Hot Countries. (London, 1904.) 

Gregory, J. W.: White Labor in Tropical Agriculture, in 19th Century 

Mag., Vol. LXVII, pp. 368-380. 

Ireland: Tropical Colonization, Chs. IV, V, VI. (New York, 1899.) 

Kidd: The Control of the Tropics, pp. 1-17. (New York, 1898.) 

Ripley: The Races of Europe, Ch. XXI. (New York, 1910.) 

Verner: The White Race in the Tropics, in World's Work, Vol. XVI, pp. 

10715-10720. 

Verner: The White Man's Zone in Africa, in World's Work, Vol. XIII, pp. 

8227-8236. 

Wallace: Natural Selection and Tropical Nature. (London, 1895.) 
Ward: Climate, Chs. IV, VII, VIII. (New York, 1908.) 
Wilson: Conquest of the Tropics, in World's Work, Vol. XVI, pp. 10432-10445. 
Willis: Agriculture in the Tropics. (Cambridge, Eng., 1909.) 



CHAPTER X 

TYPES OF CLIMATE IN 'THE TEMPERATE (INTERMEDIATE) 

ZONES 

Areas Affected 

Extent of temperate zones. The two temperate (or inter- 
mediate) zones lie on either side of the tropical zone. Denned by 
latitude, their equatorial limits are the parallels 23^2° N. and S. 
respectively, and their poleward limits the polar circles, 66^° N. 
and S. There is, however, no marked change in climate as these 
boundary lines are crossed. The intermediate zones contain a little 
more than half (52.7%) the area of the earth. 

Southern hemisphere. Land and water are distributed very 
unequally in the temperate zones. In the southern hemisphere, water 
prevails (Fig. 100), but the zone covers parts of Africa, South 
America, Australia, and various islands, of which Tasmania and 
New Zealand are most important. 

The largest land area in the south temperate zone is in South 
America, about one-fourth of the continent (or about 1,800,000 
square miles) being south of the Tropic of Capricorn. This area 
includes most of Argentina and much of Chile, and supports about 
one-fourth of the population of the continent (about 10,000,000 
people). 

More than half of Australia is south of the Tropic of Capricorn, 
but so much of it is arid that it is less important than the correspond- 
ing part of South America. About three-fourths of the people of 
Australia (more than 3,000,000) live in this zone. New Zealand, 
little more than 100,000 square miles in area, has a population of 
about a million. 

Only about 7 per cent of Africa lies south of the Tropic of Capri- 
corn. This area of 700,000 to 800,000 square miles has a population 
of 5,000,000 to 6,000,000, hardly more than 4 per cent of the popu- 
lation of the continent. 

The total land area of the south temperate zone is only about 

178 



TYPES OF CLIMATE IN TEMPERATE ZONES 179 



4,000,000 square miles, and its popula- 
tion not more than 20,000,000. In other 
words, the lands of the south temperate 
zone, taken together, have an area about 
one-third larger than that of the United 
States, and a population less than one- 
fourth as great. 

The area of ocean in the south tem- 
perate' zone is about twelve times as 
great as that of the land. Hence much 
of this zone has a marine climate. The 
climates of the south temperate zone, too, 
resemble those of the tropical zone more 
than do those of the north temperate 
zone. 

Northern hemisphere. The propor- 
tions and distribution of land and water 
in the north temperate zone (Fig. 101) are 
very unlike those in the south temperate 
zone. In the former, the area of land 
(26,000,000 square miles) is about equal 
to that of water. Furthermore, the con- 
tinents are broader in high latitudes, and 
narrower toward the equator. The north 
temperate zone contains nearly as much 
land as all the other zones combined. 
In North America, it includes all of the 
United States except the northern part 
of Alaska, most of Canada, and part of 
Mexico. Nearly all of Europe, most of 
Asia, and part of northern Africa lie 
within it. It contains the greatest na- 
tions and the majority of civilized people. 
Because of its greater expanse of land, 
continental climates are more promi- 
nent than in the southern hemisphere. 
Hence, the two zones differ greatly in the 
details of their climates. Only in cer- 
tain broad aspects can they be discussed 
together. 



■g '$ 


•0 
*> *° 




<\ 


V- 




1 


11 




m 


t 




' / 






f 






i 






! 






- |\ 


* 




I 1 






fe. t 


- 




m 






\[ 






\\ 






» 








\ 




^^ 


1 \ \ 


Vin 






H^ 




I 








/ 1 






; 






\ 


\ 










m § 


\ ' s 





d-d 






03 



O 

u 

<L> 

ci u-, 

,<U O 
U 

«J . « 

>- d 



cd 

bo 
d 

o 
,d 

£c 

N £ 
4-) xn 



c3 <u 



i8o 



ELEMENTS OF GEOGRAPHY 




-tM$^ 




^ 



'Ho 



i2G 



a + 
N c 



o cu 



General Characteristics of Climates 
of the Temperate Zones 

Variability. There are several types 
of climate in these zones, and their differ- 
ences are perhaps as striking as their like- 
nesses. Variability is the distinguishing 
feature of most of them. The climates 
vary greatly (i) in temperature, (2) in 
direction and velocity of wind, and (3) in 
amount and distribution of rainfall. In 
general, the variability is less in the south 
temperate zone than in the north temper- 
ate zone (Why?). 

Sun influence. The fundamental 
cause of variability, as contrasted with 
the uniformity of tropical climates, is 
found in the great variation in the alti- 
tude of the sun and in the length of day 
and night. The sun never is overhead 
within these zones, and during at least a 
part of the year it is many degrees below 
the zenith at noon (pp. 20-21). There 
are, accordingly, marked differences in the 
amount of heat received at different 
times, and the year is divided naturally 
into seasons which vary much in tem- 
perature. 

Influence of variable winds. The 
prevailing (westerly) winds of these zones 
are much less regular in direction and 
velocity than the trade-winds of the 
tropical zone, and are interrupted, mod- 
ified, or overcome entirely for a time, by 
cyclonic storms. The latter vary greatly 
in frequency and strength. 

Weather and climate. In the tem- 
perate zone, weather and climate are en- 
tirely different. In summer, the weather 
often resembles that of the tropics. Then 
diurnal changes (p. 78) are interrupted 



TYPES OF CLIMATE IN TEMPERATE ZONES 181 



least by storms. The temperature may 
show a regular rise and fall, day after day, 
and convectional showers may appear in 
the afternoons. These and other niinor 
features, as diurnal changes of pressure 
and wind velocity, are similar to those of 
the tropics. Cyclonic storms, however, 
may be important weather controls even 
at this season. In winter, diurnal changes 
are interrupted frequently, for then the 
chief control of weather is the movement 
of storms (p. 136). Their coming causes 
changes of temperature, changes from 
clear to cloudy skies, and changes from 
dryness to rain or snow. In the inter- 
mediate seasons, there is a gradual transi- 
tion from one control (diurnal) to the 
other (cyclonic). Thus, as spring comes 
on, the cyclonic-storm control gradually 
weakens, and the diurnal control becomes 
stronger. In the autumn, the diurnal 
control is interrupted more and more 
frequently as the cyclonic-storm control 
becomes steadily stronger. 

Temperature ranges. The factors 
noted above lead to great variability of 
temperature from day to day, from year to 
year, and from place to place. The great 
and sudden variations of temperature 
make the term temperate somewhat inap- 
propriate for these zones. The weather 
at least is often most intemperate. In 
contrast with the conditions in the trop- 
ical zone (p. 156), observations through 
many years are necessary to get a correct 
idea of the climate of a given locality in 
the temperate zones. In the temperate 
zones, the yearly range of temperature 
(Fig. 102) is greater than the daily range 
in almost every locality. 



%: 



7$ 



& 



^ 



cd fl 



„9^ 
N o 



182 ELEMENTS OF GEOGRAPHY 

In the same latitude, conditions vary widely from place to place, 
both with respect to variation of temperature, and the time of greatest 
heat and cold. Far inland, the highest and lowest mean temperatures 
of the year ordinarily occur about a month behind the highest and 
lowest noon-altitudes of the sun, and may differ by 50 , even in 
middle latitudes (as at Chicago). Spring and autumn are much alike 
so far as temperature is concerned. Near the sea, the highest and 
lowest temperatures are about two months behind the sun, while 
spring is cold and autumn is warm. The maximum temperatures in 
summer (Fig. 102) in many cases exceed those of some tropical sta- 
tions (Fig. 93), and the lowest temperatures in winter approach polar 
cold (Fig. 112). The average annual range, however, is as low as 20 
in some places, even in comparatively high latitudes. Hence, latitude 
is not a sure index of climate in this zone. 

South temperate zone. The limited extent of land in the 
south temperate zone gives it a climate less variable than that of the 
corresponding northern zone. The lands of the temperate zone in 
South America, for example, have a range in latitude of more than 
30 , but the difference in mean temperatures, between the extremes 
of latitude, is less than 30 , as shown below. 

Lat. Mean Annual Warmest Month Coldest Month 

Asuncion 25 16' 71.7 78.8 62. f 

Punta Arenas. ... 53° 10' 43.3 50 35-4° 

Difference 28.4 28.8 27.3 

This difference between Asuncion and Punta Arenas is as great as 
any to be found in settled portions of the south temperate zone. 

North temperate zone. In the northern hemisphere, on the 
other hand, the great expanses of land, and their extension into high 
latitudes, lead to marked contrasts in temperature between the two 
margins of the zone. In many places the differences are nearly twice 
as great as those of the southern hemisphere. The temperatures of 
Matamoras, Tex., and Norway House, Canada, afford a good con- 
trast, since these stations are in latitudes corresponding to those in 
South America, cited above: 

Lat. Mean Annual Warmest Month Coldest Month 

Matamoras 25 50' 73. f 84.7 6o° 

Norway House. . . 53° 50' 28.4 63. 5 

Difference 45-3° 2I - 2 ° 53° 






TYPES OF CLIMATE IN TEMPERATE ZONES 183 

Some of the highest as well as some of the lowest known tempera- 
tures occur in this zone (Fig. 102). Temperature ranges also vary 
greatly. The mean annual range of temperature in North America, 
for example, varies from as little as 16 in southern California (San 
Diego, near the sea), to as much as 8i° in northwestern Canada (Fort 
Chippewyan, far from the sea to. windward). 

Temperature and seasons. The variations of temperature in 
the intermediate zones give four seasons, which are more distinct in 
the northern hemisphere than in the southern. Near the tropical 
margins of these zones, summer and winter are less unlike than else- 
where, and the intermediate seasons, spring and autumn, are long. 
Toward the poleward margins of these zones, on the other hand, 
differences between summer and winter are great (especially in the 
north), and the transition seasons are short. Hence the length of the 
growing season for plants differs greatly in different parts of the zone, 
with important effects on life. 

Seasons and rainfall. The variations of temperature are 
accompanied by variations in rainfall. In tropical lowlands, where 
temperatures always are high, it makes little difference to vegetation 
when rain comes; but where there are seasons of radically different 
temperatures, rain is useful to plants in summer, but not in winter. 
There are two general types of seasonal rainfall in the temperate 
zones, the marine or winter type, and the continental or summer type. 
In general, windward coasts have the winter type of rainfall, while 
interiors and leeward coasts have the summer type. 

Effect of seasons on life. Both the variations of temperature 
and the distribution of rainfall have far-reaching effects on life, some 
of which may be pointed out. Civilization, which apparently began 
close to the tropics, has moved steadily outward (especially north- 
ward), until its chief centers are now in the middle latitudes of the 
northern hemisphere (p. 179). Here the seasons are commonly 
regarded as responsible for much of the energy, thrift, and industry 
which have brought about this advanced development. Seasonal 
variations of temperature are better for human development than the 
monotonous heat of tropical regions, or the depressing cold of polar 
regions. 

The changes of seasons stimulate effort. In summer, conditions 
of existence in many parts of the temperate zones are almost as easy 
as in tropical regions. Summer is a time of abundance, and winter 
is a time of scarcity in Nature's supplies. In summer, it is necessary 



1 84 



ELEMENTS OF GEOGRAPHY 



iu. 



c q 



*3 £ 



S o 



c^ 



*o7 



^ £ 






to provide food, clothing, and shelter for 
winter, when nature does not provide. 
In order to live, therefore, man must plan 
for the future, and to secure the things he 
needs requires regular effort. Life is, as 
a rule, neither too easy nor too hard. 
Careful planning and steady labor make 
it possible for man to secure what he 
needs. These conditions lead to mental, 
physical, and industrial development, and 
such development is the basis for advance 
in civilization. 



Types op Climate 

As already noted, the temperate zones 
have various types of climate. The north 
temperate zone especially is a patch-work 
of climatic types, whether the division is 
based on temperature or rainfall. The 
south temperate zone, with its smaller 
land areas, mostly near the sea, has few 
important types of climate. In the 
southern hemisphere, also, the westerly 
winds are developed better, because of 
the greater expanse of water there. 

The chief climatic types of both hemi- 
spheres are determined by (i) distribution 
of land and water, (2) winds, and (3) 
altitude. With insolation, these factors 
control the temperature and rainfall. On 
this basis, the following important types 
of climate are recognized: (1) That of 
windward coasts in low latitudes, or the 
sub-tropical type; (2) that of leeward 
coasts in low latitudes; (3) that of wind- 
ward coasts in high latitudes (above 40 ); 
(4) that of continental interiors, a type 
which varies much, especially in amount 
of rainfall; and finally, (5) the modifica- 



TYPES OF CLIMATE IN TEMPERATE ZONES 185 



tions, particularly of the continental type, 
brought about by altitude. 

I. THE CLIMATE OF WINDWARD COASTS IN 
LOW LATITUDES (BELOW 40°) 

General characteristics. The chief 
features of this type of climate are mod- 
erate temperatures, with small annual 
(Fig. 102) and large diurnal range. In 
these respects the climate resembles that 
of the tropics. The rainfall is rather light 
in most places (Fig. 69), but not in all, 
and is greatest in autumn and winter 
(Figs. 103 and 104). The summers are 
dry. This climate is typically sunny, 
usually with a maximum of cloudiness in 
winter. Winds are the chief control. 

Distribution. The sub-tropical type 
of climate is found at and near the equa- 
torward margins of the temperate zones, 
in latitudes affected alternately by the 
trade- winds, the tropical belts of high 
pressure, and the westerly winds. This 
type of climate is developed best on 
islands and on the western (windward) 
coasts of continents between the parallels 
of about 25 and 40 . It prevails over 
much of the land of the south temperate 
zone (Fig. 104), and affects extensive 
areas in the north temperate zone. It is 
widespread about the Mediterranean 
Sea, extending from Spain on the west 
through Italy and the southern part of 
the Balkan Peninsula into western Asia, 
as well as across the northern part of 
Africa. The wide extent of the sub-trop- 
ical climate about the Mediterranean has 
led to the name " Medit erranea n climate." 
In North America, the sub-tropical 
type of climate is almost confined to the 



h'Qgg 




•"<; 



•S * 



S.-a 



xi*a 



as 



N-5 



Li M 

fl Pa 

»- S3 



£% 



186 ELEMENTS OF GEOGRAPHY 

coastal part of southern California, south of San Francisco. The 
climate of this region may be taken to illustrate the type. 

The southward migration of the wind systems in winter brings 
southern California under the influence of westerly winds. The 
northward migration of the wind systems in summer brings this 
region under the influence successively of (i) greatly weakened wester- 
lies, (2) the tropical high-pressure belt, and (3) the northern margin 
of the trade-winds. 

Temperatures. This succession of winds gives moderate and 
fairly uniform temperatures (Table I). The latitude is high enough 
to prevent a long continuation of temperatures as high as those of the 
tropics, and nearness to the sea prevents the seasonal' extremes 
characteristic of most places in the temperate zones (Fig. 102). 
Freezing temperatures occur but rarely in low altitudes. The small 
daily ranges of temperature are greater than the yearly ranges. On 
the whole, the temperature of southern California is much like that 
of tropical lands at moderate altitudes. 

In some respects the sub-tropical type of climate is the best in 
the world, and is described frequently as being like "perpetual spring." 
It is healthful, as indicated by the popularity of southern California, 
where Pasadena, Riverside, San Diego, and other cities duplicate, on a 
small scale, the noted resorts in the Riviera of southern France and 
Italy. The sunny skies (68 per cent for San Diego) are an important 
factor in the popularity of these places, especially in autumn, winter, 
and spring. The dry season (summer) may be disagreeable because 
of (1) high temperatures, (2) the drying up of vegetation, and (3) the 
prevalence of fogs and dust. Numerous stations in California have 
less sunshine in the dry season than in the rainy season, on account of 
fogs. In many places it is chilly and disagreeable, at the height of 
the rainy season. 

The temperatures of San Diego, Cal. (Table I), are typical for 
western coasts in the sub-tropical zone. The absolute lowest tem- 
perature at San Diego is 32 , and the absolute maximum 101 . Such 
variations are characteristic of tropical districts where the average 
annual range is not more than 15 or 20 . Interior stations, like 
Needles and Bakersfield, show greater average ranges and more 
marked extremes, because' they are farther from the sea, with moun- 
tains between. The mean maxima are higher, the mean minima are 
lower, and the frequency of both high and low temperatures much 
greater. 



TYPES OF CLIMATE IN TEMPERATE ZONES 187 



Table I 
Sub-Tropical Climate — Mean Monthly Temperatures 

Average for 
Lat. Jan. Mar. May July Sept. Nov. Year 

San Diego 32 43' 54° 56 62 68° 66° 59 6i° 

Eureka 40 48' 47 48 52 56 56° 51 52 



Ranges and Extremes of Temperature 



Lat. 

San Diego 3 2 ° 43 

Needles 1 34° 50 

Visalia 1 36 20 

Santa Cruz 36 57 

Eureka 40 48 



Mean 






Mean 


Mean 


Abs. 


Abs. 


Ann. 


Jan. 


Tulv 


Max. 


Min. 


Max. 


Min 


6i° 


54° 


70 02 


7i° 


54° 


IOI° 


32° 


' 73° 


52° 


94° 


85° 


6o° 


116 


23° 


6i° 


44° 


8o° 


78° 


45° 


"3° 


1 7° 


' . 58° 


Si° 


64° 


69° 


42° 


108 


2 2° 


' 52° 


47° 


56° 


67° 


39° 


85° 


20° 



Rainfall. As in most similar localities (Fig. 69), the precipitation 
is rather low in southern California (Table II below), with a marked 
winter maximum. The summers are almost rainless for a period 
which varies considerably from place to place. Thus, San Diego 
(Table II) has four months (June to Sept.) with very little rain, while 
Eureka, farther north, has but two such months (July and Aug.). 
The interior valley of California is dry at all times, because the coast 
ranges have taken the moisture from the winds from the ocean. 
The dryness increases the range of temperature in the valley. In 
northern Egypt, in similar latitudes, the rainless season lasts nearly 
eight months, while sub-tropical islands, like Madeira, Lat. 32 38', 
may have a dry season (with some rain) of only two or three months. 
The distribution of rain in subtropical latitudes . therefore varies 
widely. 

Table II 

Sub-Tropical Climate — Rainfall (inches) 

Jan. Mar. May July Sept. Nov. Year 

San Diego 1.6 1.4 0.4 0.1 0.1 0.9 9.4 

Santa Cruz 5.0 4.0 1.0 T 0.5 2,7 26.8 

Eureka 7.6 6.2 2.8 0.1 1.4 5.4 458 

Needles 0.6 0.2 0.1 0.4 0.1 0.2 2.7 

T = trace of rainfall. 

1 Interior stations, to show contrast. 

2 August mean. 



Total 


Total 


(driest year) 


(wettest year) 


4-3 


27-5 


14.0 


44-3 


30.9 


59-5 


r.8 


4-7 



188 ELEMENTS OF GEOGRAPHY 

Extremes of Rainfall (inches) 
Mean Ann. 
Rainfall 

San Diego 9.4 

Santa Cruz 26.8 

Eureka " 45-8 

Needles . 2.7 

Rainfall and crops. During the rainless season, most vegeta- 
tion dries up unless irrigation is practiced. Where water is available, 
the abundance of sunshine and the favorable temperatures lead to 
extensive irrigation, as in southern California, and in the favored 
parts of southern Europe, western Asia, and northern Africa. Most 
of the crops of these latitudes, however, are grown during the rainy 
winter season, and are harvested in spring, before, or soon after, the 
beginning of the dry season. Winter crops are made possible by the 
temperatures of that season. Winter wheat is a common cereal crop 
in Italy, southwestern Australia, and California, while barley, 
resistant to both heat and dryness, was long the chief cereal in such 
climates. Corn cannot be grown without irrigation, for it needs a 
high temperature (such as that of the dry season) during growth. 

The characteristic crop of the sub-tropical climate is fruit. Or- 
anges, lemons, olives, dates, figs, and grapes are produced abundantly 
in southern California, the Mediterranean lands of Europe, north 
Africa, and Asia Minor. There is possibility of frost, however, and 
frost-fighting is an important part of the business of the California 
fruit-grower. In many sub-tropical localities, fruit-drying is an im- 
portant industry, favored by the dry, sunny weather which follows 
the ripening of the fruit. 

2. CLIMATES OF LEEWARD COASTS IN LOWER LATITUDES 

Rainfall. Leeward coasts in the temperate zone between latitudes 
25 and 40 have a climate very different from that just described. 
(1) Rainfall is heavier; (2) there is more rain in summer than in winter 
(Fig. 103) ; and (3) there is no pronounced dry season. There are occa- 
sional droughts, but they are not of regular occurrence, and are rarely 
severe. On the eastern coasts, most of the summer rains are asso- 
ciated with oceanic winds, and are of the thunder-storm type. 
Cyclonic storms also give some rain in summer, and are the principal 
cause of winter rains. Southeastern United States and southeastern 



TYPES OF CLIMATE IN TEMPERATE ZONES 189 

Asia receive occasional downpours in late summer and early autumn, 
from tropical cyclones. 

Temperature. The eastern coasts also differ from the western in 
having greater ranges of temperature, both daily and seasonal. 
Table III gives monthly data for Charleston, S. C, and, by way of 
contrast, for San Diego. 

Table III 
Leeward Coast — Low Latitudes 
Temperature 
Lat. Jan. Mar. May July Sept. Nov. Year 

Charleston 32° 4 7' 5°° 58° 73° 82 76 58 66° 

San Diego 32° 43' 54° S6° 62 68° 66° 59 6i° 

Rainfall (inches) 

Jan. Mar. May July Sept. Nov. Year 

Charleston 3.6 3.8 3.6 7.4 5.5 3.0 53.4 

San Diego 1.6 1.4 0.4 0.1 0.1 0.9 9.4 

In southeastern United States, sudden and extreme changes of 
temperature are especially frequent in winter. The contrast between 
southern California and South Carolina (in the same latitude) is due 
to the fact that the temperature of the eastern coast is not affected 
so much by winds from the ocean (Why?). At San Diego the 
lowest temperature recorded is 32 , and this but once in ten years. 
At Charleston, the lowest temperature recorded is 7 , while tempera- 
tures below 3 2 occur many times every year. Even as far south as 
Tampa, Lat. 27 57', freezing temperatures occur in most years. 
This greater frequency of temperatures below freezing is due to anti- 
cyclones (p. 136). For the farmer and fruit-grower of Florida and 
the Gulf district, frost is an even more serious factor than in 
California. 

The eastern coasts of southern continents suffer much less from 
frosts than those of the northern hemisphere. This is because in the 
southern hemisphere there are no broad land masses in higher lati- 
tudes, from which cold winds may blow to lower latitudes. 

The summer temperatures of leeward coasts in low latitudes are 
much like those of equatorial regions. The day-time temperatures are 
in many cases fully as high as in the tropics, and there is less relief at 
night, since the nights are shorter in the higher latitudes at this sea- 
son. The humidity also is high (Fig. 44), owing to the summer rains; 
consequently, the sensible temperatures are much higher than those 



i 9 o ELEMENTS OF GEOGRAPHY 

of the dry sub-tropical climates. These conditions are shown by 
contrasting Charleston and Savannah with Para, Brazil: 

Warmest Month 

T Mean Mean Mean TT ... 

Lat - Temp. Max. Min. Humidity 



Para, Brazil i° 30' S. 79-5° 93- 2 ° 71. 6° °4/o 

Charleston 32° 4 7'N. 82 88° 76 70% 

Savannah 32°3' N. 82 90 74 82% 

Effect on life. Near the equatorward margins of the areas 
having this type of climate, conditions favor the production of sub- 
tropical or even so-called tropical crops. Sugar-cane, rice, and cotton 
are common products of the southeastern coastal lands of the United 
States, and cotton of the interiors. In this part of the United States, 
for example, is the greatest cotton belt in the world (p. 547), but while 
the cotton plant of the tropics may produce for some 20 years, the 
cotton plant of these latitudes is killed by frost every year (Fig. 109). 
The corresponding section of southeastern Asia produces much rice. 
Some sub-tropical fruits also grow in the more favored sections of the 
east coasts. Thus Florida grows many oranges. Forage crops will 
grow in a large part of southeastern United States for ten or eleven 
months in the year; hence it is a region in which some. phases of the 
dairying industry might be developed highly. 

The abundance of rain on eastern coasts favors the development 
of swamps. Where there are high temperatures, these swamps 
invite diseases like those of equatorial regions (malaria, yellow fever, 
etc.). The home of malaria in the United States is on the low plains 
and in the river valleys along the eastern coast south of New York 
(p. 460). Tropical diseases have been brought into these sections 
and have become established there during the hot, damp season. 
Thus yellow fever has been introduced many times into the Gulf and 
South Atlantic ports of the United States from the nearby tropics, but 
it never lasts from one summer to the next, on account of the frosts in 
winter (Fig. 109). 

The effect of this climate on people resembles that of equatorial 
climates. The enervating effects of heat and humidity are obvious. 
Work in the fields, through much of the year, is not agreeable to white 
men ; hence climatic conditions favored the development of slavery in 
the southern states. The mild winters, however, attract many people 
who seek to escape the rigor of more northerly latitudes. 



TYPES OF CLIMATE IN TEMPERATE ZONES 191 

3. CLIMATE OF WINDWARD COASTS IN HIGH LATITUDES (ABOVE 40°); 

MARINE CLIMATE 

Location. The marine type of climate in the temperate zone is 
confined to islands and windward (western) coasts above the 40th 
parallel. It is controlled by prevailing westerly winds blowing almost 
constantly from ocean 'to land. The transition from the sub-tropical 
climate (p. 185) to the marine type is gradual, and in certain respects 
they are not very unlike. 

In the western hemisphere, the marine type of climate is developed 
best (1) from San Francisco to the Arctic Circle, and (2) in Chile, 
south of latitude 40 . In North America, it is confined to the area 
west of the Cascade, Klamath, and Sierra Nevada mountains, and is 
modified greatly east of the low coast ranges. In Chile, it does not 
extend east of the Andes Mountains (Fig. 104). 

In the eastern hemisphere, it does not appear in South Africa or 
Australia, because neither extends into high enough latitudes. It 
affects parts of Tasmania and most of New Zealand. In northwest- 
ern Europe it affects the coast from France to the Arctic Circle, and 
extends 'far inland, because there is no continuous north and south 
mountain range to extract moisture from the westerly winds. Hence 
the transition from marine to continental conditions is very gradual, 
and the influence of the sea is felt almost to the Russian frontier. 
From the British Isles eastward through Germany, the annual 
rainfall decreases gradually, the winter maximum is replaced 
by spring and summer maxima (Fig. 103), and the ranges and 
extremes of temperature become more marked (Fig. 102). The tem- 
pering effect of the westerly winds on the climate of western Europe is 
the more pronounced, because of the relatively high temperature of 
the central and eastern parts of the North Atlantic Ocean. 

Temperatures. The variations of temperature are less than in 
the same latitudes elsewhere (Fig. 102). Thus, the yearly range of 
temperature even in high latitudes (as Sitka, Alaska, Lat. 57 ) may be 
as little as 25 , a range hardly more than that in some parts of the 
tropics. Thorshaven, in the Faroe Islands, Lat. 62 , has a range of 
only 14. 2 . In this respect the marine climate in the temperate zone 
resembles the sub-tropical type, though the actual temperatures are 
lower (Why?). Astoria, Ore. (Table IV), furnishes a good example 
of the temperatures of this type of climate — the only really temperate 
climate of the intermediate zone. 



192 ELEMENTS OF GEOGRAPHY 

Table IV 



Marine Climate— 


-Temperature and Rainfall 






Lat. Jan. 
Astoria, Ore. . . . 46 n' 41 
Rainfall, inches.. • 11.1 


Mar. May July Sept. 
46 54° 6i° S9° 
7.7 4.1 1.1 3.7 


Nov. 

47° 

11. 8 


Year 

52° 

78.2 


Interior Climate- 


-Temperature and Rainfall 






Lat. Jan. 
Moxee Wells, 1 Wash. 46 2' 30 
Rainfall, inches 1.9 


Mar. May July Sept. 
42 58° 7i° 59° 
0.5 0.9 0.1 0.4 


Nov. 

39° 

i-3 


Year 
8.9 



Regions having a marine climate have mild winters and cool 
summers, and their average yearly temperatures are higher than the 
average of other regions in the same latitude. For example, Ireland, 
which represents perhaps the extreme case, is 30 or 40 too warm for 
its latitude, 55 N. Another contrast is found in comparing Sitka, 
Alaska, with Nain, Labrador, in about the same latitude, and with 
Philadelphia, in a much lower latitude near the leeward coast: 

Mean Temp. Mean Temp. 

Lat. Jan. July Ann. Range 

Sitka, Alaska, west coast . . 57° 3' 30. 2° 54-5° 24. 3 

Nain, Labrador, east coast. 56° 33' 7.2 48. 3 41 .i° 

Philadelphia, east coast .. . 39 56' 32 76. o° 44 .o° 

Rainfall. Places freely exposed to westerly winds have abundant 
rainfall during that part of the year when the land is cooler than the 
sea. This means a dry (but not rainless) summer (Figs. 103 and 107) 
where lands are low, though the dry season is much shorter than in 
lower latitudes (Why?). High western coasts have abundant rain- 
fall, high humidity, and cloudiness all the year. In some localities 
fogs occur almost daily, and in extreme cases, as along the coast of 
Alaska, they may persist for weeks at a time. A typical develop- 
ment of these conditions is found on the coasts of Oregon (Astoria, 
Table IV) and Washington, where the heaviest recorded rains of this 
country occur. The precipitation at Glenora, Oregon, averages 136 
inches. The humidity always is high (Fig. 44), the mean annual 
cloudiness is 75 to 80 per cent (Fig. 50), and evaporation is extremely 
low (Fig. 43). The typical marine locality is cool, damp, and rainy. 

Though the maximum precipitation is in winter, little of it is in 
the form of snow, except at high altitudes. In this respect west 

x Near North Yakima, Wash., about 250 miles from the coast. 



TYPES OF CLIMATE IN TEMPERATE ZONES 193 

(windward) coasts are in contrast with east (lee) coasts (Table V), 
where places as far south as Baltimore receive much more snow 
than places in corresponding latitudes on the western coast (Fig. no). 

Table V 
Snowfall (Monthly averages in inches) 

Astoria Eastport, Me. Philadelphia 

Lat. 46 11' Lat. 44 54' Lat. 39 56' 

November 0.3 7.4 1 . o 

December 1.0 12.9 3.3 

January 3.5 15.9 6.1 

February 2.2 18.6 7.7 

March 1.1 13.5 3.7 

April 0.0 



0.4 



22. 2 



Year 8.1 77 

The contrast between the summer rainfall of the temperate and the sub- 
tropical parts of western coasts is illustrated well on th*e Pacific coast of the 
United States, which shows an increasing amount of rain in summer to the north- 
ward. At San Diego, Lat. 32 43', typical sub-tropical conditions are illustrated 
by a total rainfall of 0.4 in. from June to September; Santa Cruz, Lat. 36 57', 
has 0.7 in.; Eureka, Lat. 40 48', 2.8 in.; while Astoria, Lat. 46 n', has 9.4 in. 
during the same months. San Diego during six months (May to October, p. 187) has 
hardly more than one inch of rain. In Eureka, two months (June and July) are 
nearly rainless, but at Astoria the rainfall of no month averages as low as one inch 
(p. 192). Astoria has as much rain during its driest month, as San Diego has in its 
driest six months. 

Effect on life. The combination of cool summers, abundant 
moisture, and much cloudiness, prohibits the growth of many kinds of 
crops. For example, in the typical marine localities of western North 
America and northwestern Europe, wheat and corn are not grown. 
Wheat requires a dry, sunny harvest season, and so its growth near the 
coasts under consideration is confined to localities where topography 
modifies marine conditions, as in eastern Washington and eastern 
England. Corn needs a higher temperature and more sunshine than 
the marine climates afford. Oats, rye, and barley, however, are 
grown successfully in a cloudy, damp climate. This is perhaps the 
chief reason why oats have furnished the staple food of Scotland. 
Various crops are grown close to the northern limit of the intermediate 
zone in northwestern Europe and in Alaska. Thus in Norway, rye, 
oats, barley, and potatoes are grown successfully within the Arctic 
Circle. In Alaska, barley, potatoes, cabbage, and turnips have been 
grown at Ft. Yukon, Lat. 66° 30'. The marine climate is also favor- 



i 9 4 ELEMENTS OF GEOGRAPHY 

able for grass, which in some localities grows ten or eleven months in 
the year (Fig. 109). For this reason, the raising of live stock is or may- 
be important in this climate. In the British Isles, for example, the 
grazing industry has long been the leading phase of agriculture. 
Mild temperatures and abundant moisture make Ireland always 
green (Emerald Isle), and the raising of cattle is a chief industry. 

Marine climate also favors the growth of heavy forests, which 
must be cleared before the land can be cultivated, and the clearing 
is difficult and expensive, in many places costing as much as $100.00 
per acre, after the valuable timber is cut. Good examples of such 
forests are found in northwestern United States (p. 557). North- 
western Europe was originally well forested under similar climatic 
conditions, and southern Chile is now. In forested regions, lumbering 
is likely to be an important industry, and forest products are leading 
articles of trade. In these same localities, also, mountains near the 
coast cause heavy precipitation, much of which is in the form of snow. 
The melting of these snows in summer keeps the streams full, even 
when the rainfall is least. Mountain streams afford water power, 
which favors the handling of timber. Among native tribes, forest 
conditions lead to hunting and fishing as regular pursuits. 

The change of climatic conditions with increasing latitude has 
resulted in significant contrasts in the occupations of the people along 
the west coast of both American continents. Chile, which extends 
through more than 35 of latitude, affords a good illustration. In the 
northern part of this country, there is a coastal desert near the margin 
of the trade- wind zone. Here conditions have favored the accumula- 
tion of guano and nitrate deposits, which have been the basis of im- 
portant industries and commerce, and the cause of bitter strife 
between Chile and Peru. South of the desert, the sub-tropical type of 
climate has led to irrigation and the growth of fruits. Still farther 
south, where the climate is of the type under consideration, grazing 
and the raising of cereal crops and vegetables are the chief occupa- 
tions. In the extreme southern part of the country, the heavy rain- 
fall from the westerly winds supports luxuriant forests, and forest 
industries and fishing are the chief occupations. Similar contrasts 
exist along the western coast of North America from California north- 
ward, and along the coast of Europe from Spain to Norway. If the 
marine influence did not penetrate far inland, the densely populated 
and highly developed countries of western Europe, especially north of 
latitude 50 , would be far less important than now. 



TYPES OF CLIMATE IN TEMPERATE ZONES 195 



4. CONTINENTAL CLIMATES 

Regions affected. The contrast in climate between the conti- 
nental interiors and the windward coasts of the temperate zone is due 
to (1) the fact that land absorbs and radiates heat more readily than 
water, (2) the effect of topography, (3) greater distance from the sea 
to windward, and (4) cyclonic storms. 

The continental climate is not developed in the south temperate 
zone, except in the southern part of Argentina. North America and 
Eurasia, on the other hand, have their greatest width in rather high 
latitudes (Fig. 101), and this favors the full development of conti- 
nental climates. In North America, there is a sharp transition inland 
from the marine climate of the western coast to the continental 
climate of most of the United States and Canada. In Eurasia, the 
conditions already noted (p. 191) limit the continental type of climate 
chiefly to the Russian Empire and the interior of China. 

Temperatures. The first and most pronounced characteristic of 
the continental climate is extremes of temperature (Fig. 102). The 
winters are cold, the degree of severity increasing (1) with the latitude, 
and (2) with increasing distance from the sea to windward. In lati- 
tude 45 , in North America, the lowest temperatures are about — 3o°F. 
Farther north they are still lower, reaching — 6o°, or even less, near the 
northern limit of the zone. A great area in northeastern Asia, far 
from the ocean to windward, has extremely low temperatures in 
winter (Fig. 102). 

Only in the northern part of the United States does the tempera- 
ture ever fall to — 40 . But, except in the Gulf region, there is no 
large section east of the Pacific coast where temperatures of io° to 
20 below freezing do not occur every year. The summers are hot. 
July averages of 6o° are found beyond the northern margin of the 
zone, and maximum temperatures of 8o° to 90 occur close to the 
Arctic Circle (Fig. 102). In the southern part of the zone, the 
summer temperatures are almost tropical. 

The annual ranges of temperature are very great, especially for 
the northern part of the north temperate zone.- In northwestern 
Canada, the difference between the lowest and the highest tempera- 
tures of the year has reached 150 , and in northeastern Asia, 180 . 
The high mountains to windward of northwestern Canada have much 
the effect of a wide expanse of land on its climate. In the lower 
latitudes the extremes are not so great. The winters are milder, 



196 



ELEMENTS OF GEOGRAPHY 



owing to the lower latitude, but the summers are not correspondingly 
warmer. Thus in our southern states only small areas ever have 
temperatures above ioo°, and except for the immediate Gulf coast the 
mean maximum temperatures are under 90 , or no higher than those 
occasionally recorded "near the Arctic Circle. 

Cyclonic influence. The second important feature of conti- 
nental climate is the variability of weather from day to day. 




Fig. 105. Chart showing annual storm frequency in the United States. 
Numbers on lines indicate the average number of storms per year. Broken lines 
indicate mean storm tracks. (After Dunwoody.) 



Cyclones and anticyclones interrupt the prevailing westerly winds 
frequently (Fig. 105), and within the course of a few days give winds 
from all points of the compass. Each wind tends to bring its own 
distinctive weather conditions. Thus, the northerly winds of anti- 
cyclones in winter carry freezing temperatures almost to the southern 
margin of the zone (Figs. 87 and 88). This is illustrated in the Gulf 
States, where a change from normal mild conditions to a temperature 
of 20 F. may occur in a single day. On the other hand, southerly 
winds carry warm air to comparatively high latitudes (Fig. 70), and 
may produce a summer-like temperature in mid- winter, even as far 
north as New York and Chicago. Cyclonic storms occur frequently 



TYPES OF CLIMATE IN TEMPERATE ZONES 197 



/f 







"J 



<! 



198 ELEMENTS OF GEOGRAPHY 






(Fig. 105) ; hence there is repeated change from clear, cold, and dry 
days, to cloudy, warm, and damp days. 

Rainfall. A third important feature of the continental climate 
is its rainfall, which is moderate or scanty (Figs. 69 and 106). In 
most places it does not exceed 40 inches a year, and most of it comes 
during the spring and summer months (Figs. 103 and 107). There is 
a tendency toward a dry season in winter, but, as a rule, some rain 
falls each month, except in desert or semi-desert regions. The 
occurrence of the maximum precipitation (Fig. 107) when tempera- 
tures are favorable for plant growth is the most important aspect of 
the rainfall. 

These temperature and rainfall conditions are associated with 
lower humidity (Fig. 44), less cloudiness (Fig. 50), and greater evapo- 
ration (Fig. 43) than go with the marine climate. In these respects the 
climate of continental interiors is more like sub-tropical climate than 
like the marine climate of the temperate zone; but the continental 
climate differs from the sub-tropical in its lower average temperature, 
and in its greater extremes. 

The rainfall of this climate is moderate, because most lands 
affected by it are (1) remote from the ocean, and (2) devoid of 
important local sources of moisture. The effect of the first point is 
illustrated by the distribution of the rainfall of Eurasia. The western 
slopes of the British Islands receive 80 to 100 inches of rain yearly; in 
Germany and western Russia, the amount is 20 to 30 inches ; in east- 
ern Russia and western Siberia, between 15* and 20 inches; while in 
central and eastern Siberia, large areas have less than 10 inches. In 
southern Siberia, in the lee of the mountain ranges of central Asia, the 
rainfall is as little as 5 inches in many localities. 

Arid and humid interiors. On the basis of rainfall, two sub- 
divisions of continental climate are recognized, the one humid and 
the other arid. The two types merge into each other through a 
zone of intermediate rainfall {semi-arid). Forests are characteristic 
of the humid climate. From dense forests, where rain is plentiful, 
there are gradations through less dense forests, to treeless tracts, 
covered with grass. Most grassy lands mark the transition from 
the humid to the arid type of continental climate. Toward arid 
regions the grassy vegetation becomes meager, and finally gives place 
to desert growths. In a general way, dryness increases with increasing 
distance from the ocean to windward; but topography and cyclonic 
storms modify this general relation. Altitude is an important factor 






TYPES OF CLIMATE IN TEMPERATE ZONES 199 




200 



ELEMENTS OF GEOGRAPHY 



in continental climate, especially in the drier tracts, because it 
increases precipitation. The increase is enough in many places to 
cause a transition from arid conditions on lowlands, to grassy lands at 
moderate altitudes, and timber still higher up. As in tropical deserts, 
this local effect of high elevation plays an important part in the life 
of the arid regions. 

Continental Climates in the United States 
The arid portion of the United States lies near the western coast 
(Fig. 1 08), because the Sierra Nevada, Klamath, and Cascade moun- 
tains stop much moisture which the winds from the Pacific Ocean 







Fig. 108. Map showing arid, semi-arid, and humid regions of the United 

States. (After Newell.) 

would otherwise bring farther inland. These mountain barriers limit 
the rainfall of about half the country to less than 20 inches a year. 
The western half of our country, therefore, is affected mainly by the 
arid and semi-arid types of climate, the drier part lying to the west, 
and the grassy (prairie or steppe) districts to the east. 

The interior of the country, therefore, may be divided into three 
areas (Fig. 108), according to the amount of rainfall — (1) the arid, 
chiefly between the Sierra Nevada and Cascade mountains on the west 
and the Rocky Mountains on the east; (2) the semi-arid, between the 
Rocky Mountains and longitude 98 to ioo°; and (3) the humid tract, 



TYPES OF CLIMATE IN TEMPERATE ZONES 201 

lying farther east. All these regions are much alike in having 
extremes of heat in summer, and of cold in winter. They also have 
great changes of temperature and humidity from day to day, as a 
result of passing cyclones and anticyclones. The difference in the 
amount of rainfall, however, makes conditions of life very different 
in the three regions. 

(1) The Arid Region 
The arid region (Fig. 108) includes most of the Cordilleran sec- 
tion of the United States, except the high mountains, on which the 
rainfall may amount to 30 or 40 inches (Fig. 106). The average 
annual rainfall is less than 15 inches, and is less than 10 inches over 
large areas. Hence much of the land is almost desert, sunshine 
prevails throughout the year (Fig. 50), relative humidity is low, and 
evaporation high. The nights are usually cool even when the days 
are hot. The heat of summer (Table VI), though frequently marked 
by high maxima (Tucson, mean max. June, ioo°), is so modified by 
the low humidity that the sensible temperatures are not very high. 
So far as the combined effects of temperature, humidity, and sun- 
shine are concerned, the arid district has an agreeable climate. 

Table VI 
Continental Climate — Arid Type 

Temperature 
Lat. Jan. Mar. May July Sept. Nov. Year 

Logan, Utah 41 44' 24 34 55° 71 55° 38 47 

Tucson, Ariz 32 14' 50 59 74 88° 8i° 59° 68° 

Rainfall (inches) 

Jan. Mar. May July Sept. Nov. Year. 

Logan, Utah 1.1 1.8 2.2 0.4 .1.1 1.1 14. 1 

Tucson, Ariz 0.7 0.6 0.1 1.8 0.8 0.7 9.8 

Extremes 
Temperature Rainfall 

July Jan. Abs. Abs. Wettest Driest 

Mean Max. Mean Min. Max. Min. year year 

Logan 86° 21 ioo° -19° 17.3 in. 12.6 in. 

Tucson 99 35 112 io° 14.6 m. 5.2 m. 

Effects of scanty rainfall. The scanty rainfall (Tucson, Table VI) 
means scanty vegetation of nearly worthless types, except where 
high altitudes cause rain enough to support grass or timber. The 
rapid evaporation of water from the ground leaves the alkaline sub- 



202 ELEMENTS OF GEOGRAPHY 

stances of the water in the soil, and the slight rainfall is not enough 
to dissolve and carry them away to rivers and thence to the sea. 
In some places this gives rise to alkaline soils, which are unfavorable 
to vegetation, and require elaborate treatment before they become 
productive. Where not alkaline, desert soils are naturally rich, 
because elements important for plant food have not been leached out 
(p. 448). Hence where water can be supplied to desert lands, they are 
usually highly productive. 

The use of the desert depends largely on the availability of water. 
Where rainfall is enough to support even a meager growth of grasses, 
the grazing industry, especially the raising of smaller animals like 
sheep and goats, is an important occupation. Many mountains 
receive much snow in winter, and this may afford water for irrigation. 
The total area which can be irrigated, however, is but a small portion 
of the entire arid district (p. 449). The tillage of soil is therefore 
not the most wide-spread industry of arid lands. 

Mining is an important industry in parts of the arid West, though 
aridity has little or nothing to do with the development of the ores. 
In some places, the absence of sufficient water or timber, or both, has 
been a severe handicap to mining. Desert conditions favored the 
accumulation of salt deposits, as about Salt Lake, and borax deposits, 
as in Death Valley, California. 

The population of the arid section is necessarily scanty, because 
there is no natural basis for permanent or extensive settlement in 
most localities. 

(2) The Semi- Arid Region 

The arid section gives way gradually to a semi-arid region lying 
east of the Rocky Mountains (Fig. 108), and west of longitude 98 
to ioo°. Here the yearly rainfallis between 15 and 20 inches (Fig. 
106), with a distinct maximum in the spring and summer months 
'(Fig. 107, and North Platte, Table VII). The tract has only one 
mountain area (the Black Hills), hence there is little increase of 
precipitation as the result of altitude, and forests are generally absent. 
The section is typically sunny and dry, with high temperatures in 
summer (Table VII), and low temperatures in winter. The sensible 
effects of the extremes, however, are moderated by the dryness of the 
air. The open character of the country favors free circulation of the 
atmosphere, and fairly constant winds of moderate to high velocity 
are more or less typical of most of the region. 



TYPES OF CLIMATE IN TEMPERATE ZONES 203- 



Table VII 

Continental Climate — Semi- Arid Type 
Temperature 



Lat. 


Jan. Mar. May 


July 


Sept. Nov. Yea 


North Platte, Neb. 41 8' 


24° 35° 59° 


74° 


63° 35° 48 c 


Abilene, Tex 32 23' 


44° 55° 72° 
Rainfall (inches) 


82 


75° 54° 6 4 c 




• Jan. Mar. May 


July 


Sept. Nov. Year 


North Platte 


0.4 0.8 2.8 


2.6 


1.4 0.4 17.9 
3-2 1.3 24.5 


Abilene 


0.9 1.3 3.8 


2.0 




Extremes 








Temperature 




Rainfall 


July 


Jan. Abs. 


Abs. 


Wettest Driest 


Mean Max. Mean Min. Max. 


Min. 


Year Year 


North Platte 86° 


io° 107 


-35° 


30 in. 11 . 1 in. 


Abilene 93 


33° n°° 


-6° 


35-5 in. 15-7 in 



Effect on life. The semi-arid district is a region of grass land, 
the rainfall being insufficient for most cultivated crops (Table VII). 
Grazing has consequently been the most general occupation, and cul- 
tivation of the soil has been restricted chiefly to river valleys (p. 495). 
A supply of water is highly prized, and not infrequently bitter contests 
have been waged over the question of ownership. Thus the use of 
the waters of the Arkansas River, which flows from Colorado into 
Kansas, was the cause of a long legal battle between the two states, 
because there was not water enough for both. 

(3) The Humid Region 
The semi-arid region merges gradually into the humid region far- 
ther east (Fig. 108). The temperatures of the latter (Ottawa, 111., 
Table VIII) are similar to those of corresponding latitudes farther 
west, but cloudiness and humidity are greater, and evaporation less; 
hence sensible temperatures are higher in hot weather. The rainfall is 
rarely as low as 20 inches a year, and most of it comes in summer (Fig. 
107). The amount of rain necessary for crops without irrigation varies 
with the latitude. More is needed in Oklahoma than in Dakota, 
because the higher temperature and lower humidity of the former 
cause greater evaporation. In the western part of this region, trees 
appear in the river bottoms; farther east, they become more abun- 
dant, and forests are found (or were once) where the rainfall is heavier. 



204 



ELEMENTS OF GEOGRAPHY 



Throughout the humid region, the rainfall is adequate for cultivated 
crops, and contains some of the greatest agricultural tracts of the 
temperate zone. 

Table VIII 
Continental Climate — H timid Type 
Temperature 
Lat. Jan. Mar. May July Sept. Nov. Year 

Ottawa, 111 41 20' 24 36 62 76 65° 39 50 

Chicago/ 111 41° S3' 24 34 S7 9 72 64 39 48 

Meridian, Miss... 32 21' 46 56 72 8o° 74 54° 64 

Rainfall (inches) 

• Jan. Mar. May July Sept. Nov. Year 

Ottawa 2.2 2.9 4.0 4.0 3.6 2.5 36.7 

Chicago 2.0 2.5 3.5 3.6 3.0 2.6 33.4 

Meridian 5.0 5.8 4.3 5.3 3.0 3.0 53-4 

Extremes 
Temperature Rainfall 

July Jan. Abs. Abs. Wettest Driest 

Mean Max. Mean Min. Max. Min. Year Year 

Ottawa, 111 89 15 112 -26 55.7 in. 26.9 in. 

Meridian, Miss. 90 37 104 -6° 72 in. 44.5 in. 

Because of the higher humidity, the high temperatures of sum- 
mer are more trying here than in the more arid regions to the west. 
The low temperatures of winter are also harder to bear than are the 
greater extremes of "dry cold" where the humidity is lower. 

Effects on life. The crops raised are determined largely by 
the climate. Wheat, for example, is raised most in the less rainy 
regions (Fig. 410), and its seed time and harvest are influenced by 
climate. In the north, spring wheat is grown, largely because the' 
winters are too rigorous for wheat sown in the autumn. Farther 
south, where the winter season is shorter and milder, both winter and 
spring wheat may be grown, the former predominating in many sec- 
tions. The harvesting of winter wheat begins in the south in June, 
and the harvesting of spring wheat ends in the north about the first 
of September. The harder varieties of wheat, rich in gluten and good 
for macaroni, are grown in the drier sections, while softer varieties, 
less rich in gluten, but good for flour, are grown where rain is more 
plentiful (p. 543). 

1 Chicago, 83 miles east of Ottawa, has a climate modified by Lake Michigan, 
as indicated by the above data. 



TYPES OF CLIMATE IN TEMPERATE ZONES 205 

The best climate for wheat is one with a dry, sunny harvest season, 
such as that of the Sacramento Valley, in California, and of eastern 
Washington (p. 193). This ideal climate is not found in much of the 
humid interior. Wheat is the standard crop only in a north-south 
belt, some ten degrees in width, just east of the 100th meridian. 
Even here, the climate is not so good for wheat as that of eastern 
Washington. 

East of the wheat belt, the heavier annual and summer rains are 
favorable for a variety of crops. Corn is the standard cereal in great 
areas (Fig. 409), though wheat, oats, and other crops are commonly 
grown in rotation with it. Most of the corn is grown south of the 
wheat belt, because c*orn requires a higher temperature, and for some 
varieties a longer warm season. With corn, many other cereals, vege- 
tables, and fruits are grown, all requiring more moisture than wheat. 

The humid continental region of the United States is the region 
of greatest development. It has the major part of the population 
(Fig. 442), it contains most of the chief cities (p. 595), its manufac- 
turing and commercial activities are greatest (p. 573), and its trans- 
portation facilities are most extensive (Fig. 440). All these lines of 
development are connected more or less intimately with the abundant 
yield from the soil, a result in large part of favorable climatic 
conditions. 

Climate of Lee Coasts in the Higher Latitudes 
Temperatures. The eastern coasts of the northern continents, 
especially in latitudes above 40 , lie in the lee of broad land areas 
(Fig. 101). In the southern hemisphere, only South America 
extends south of latitude 40 (Fig. 100), and above the 40th 
parallel that continent is nowhere more than 600 miles wide. Hence 
the leeward coast type of climate, in high latitudes, is confined chiefly 
to the north temperate zone. This type of climate is similar 
to the humid continental type, with extremes of heat, cold, and 
drought reduced. It is very unlike the climate of windward 
(western) coasts in the same latitudes. The westerly winds carry 
the continental influence to the eastern coasts, and, in fact, to islands 
off-shore. Thus St. Johns, Newfoundland, more than 300 miles from 
the mainland, Lat. 47 34', has a mean annual temperature of 41 , 
with a January mean of 24 and a July mean of 6o° (mean maxima of 
84 and mean minima of 8°). These temperatures are quite unlike 
those of Astoria (Table IV, p. 192), in nearly the same latitude. 



206 ELEMENTS OF GEOGRAPHY 

The climate of the Japanese Islands also shows the effect of the 
Asiatic land mass to the west. Thus Nagasaki, in about the latitude 
of San Diego and Charleston (Table III, p. 189), has a mean annual 
temperature of 6o°, a July average of 8o°, and a January average as 
low as 41 . The British Isles, lying in a corresponding position on 
the windward side of the Eurasian continent, but in a much higher 
latitude, do not show so great seasonal differences. (Plymouth, Eng., 
Lat. 50 , mean ann. 51.2 ; Jan. mean 42. 4 , July mean 61. 8°.) The 
climate of eastern coasts in high latitudes, therefore, is essentially 
continental. 

The larger area of Asia makes its effect on the lee coast somewhat 
greater than that of North America. Thus Vladivostok is, on the 
average, 18 colder in January than Portsmouth, N. H., in about 
the same latitude (43 5' N.). This difference is important to the 
marine commerce of the United States, for none of our important 
harbors are hampered much by ice. If the eastern coast of North 
America were as cold as that of Asia in corresponding latitudes, it 
would be blocked by ice for weeks each year, as far south as New York 
City. (Niuchwang, Lat. 40 53', Jan. mean 15 ; New York, Lat. 4o°43 r , 
Jan. mean 30 .) The Amur River, in east Asia, is ice-blocked about 
seven months a year; the St. Lawrence, but little farther north, is 
closed about five months. 

Great changes of temperature in the United States are favored 
by the paths of cyclonic storms (Fig. 105). As the latter cross the 
continent, they tend to converge toward the area lying between the 
40th parallel and the St. Lawrence Valley. Hence that coastal sec- 
tion has a most variable climate. Nevertheless the tempering 
influence of the sea is seen by comparing the temperatures of New 
Bedford (Table IX) with those of Ottawa (Table VIII), in a similar 
latitude. 

As a result of the contrast between windward and leeward coasts, 
northwestern Europe and northeastern North America, in correspond- 
ing latitudes, are radically unlike. The contrast between Labrador 
and the British Isles is striking. Labrador — cold, bleak, and unde- 
veloped — has a continental climate. The British Isles — mild, moist, 
and highly developed — show the full benefit of the moderating influence 
of the sea. The continental influence is felt along lee coasts, especially 
in winter, in comparatively low latitudes. Tampa, Florida, Lat. 27 
57', for example, has minima of 32 or lower almost every year. 
This condition affects agriculture greatly, for sugar cane, rice, and 



TYPES OF CLIMATE IN TEMPERATE ZONES 207 

many tropical or semi-tropical fruits grown in the Gulf states are 
injured severely by a freezing temperature. 

In the lower latitudes, the contrast between windward and leeward 
coasts is most marked in summer; in higher latitudes, it is greatest in 
winter (Why?). This may -be seen by comparing the stations in 
Table IX with those in similar latitudes on the Pacific coast (p. 187). 

Table IX 

Continental Climate — East Coast 
Temperature 
Lat. Jan. Mar. May July Sept. Nov. Year 

New Bedford, Mass 41° 39' 28 34 55° 6o° 62 41 48 

Charleston, S. C 32 47' 50° 58 73 82 76 58° 66° 

Rainfall (inches) 

Jan. Mar. May July Sept. Nov. Year 

New Bedford 4.4 5.1 3.9 3.4 3.4 4.4 47.9 

Charleston 3.6 3.8 3.6 7.4 5.5 3.0 53.4 

Extremes 
Temperature Rainfall 

July Jan. Abs. Abs. Wettest Driest 

Mean Max. Mean Min. Max. Min. Year Year 

New Bedford. . 77 20 94 -u° 62.6 m. 43.6 m. 

Charleston 88° 43 104 f 78.4 m. 29.7 m. 

The influence of the ocean is felt along the east coasts chiefly in 
two ways. First, the summer temperatures are somewhat cooler 
(Fig. 102), particularly above the 45th parallel, because of frequent 
winds from the oceans. This cooling influence is felt less in the 
United States than in Canada, especially in Labrador. Hoffenthal, 
in southern Labrador, has a July mean of only 49. 8°, as compared 
with 63. 5 at Norway House, at the northern end of Lake Winnipeg. 
The latter is near the great Canadian wheat district. In Labrador 
none of the cereals will ripen. The meager population therefore 
finds its chief support in fishing, hunting, and trapping. Fishing 
especially is important during the summer, and when the catch is 
small, the people suffer greatly from want during the long, cold 
winter. 

Shore towns in nearly all latitudes feel the beneficial effects of the 
sea-breeze (p. 114), and many important sea-shore resorts from New 
Jersey northward are the result. 



208 ELEMENTS OF GEOGRAPHY 

Rainfall. A second effect of the ocean is on the rainfall. Both 
North America and Asia (Fig. 69) show an increase in the amount 
of rainfall as the lee coast is approached. Under varying local con- 
ditions, a slight maximum may appear in almost any season. 
Summer maxima are most common in middle latitudes, but winter 
maxima are common in high latitudes. A belt where the rainfall 
exceeds 40 inches lies parallel to the eastern coast of the United States 
throughout its entire length. This is due to the in-draught of air 
from the ocean during the movement of cyclonic storms. Indeed, 
the entire eastern half of the United States depends for its plentiful 
rain on cyclones (p. 132). 

The same factors which increase the rainfall along our eastern 
coast increase also humidity (Fig. 44), cloudiness (Fig. 50), and fog, 
and so lower the rate of evaporation (Fig. 43). Places exposed freely 
to the sea (like Newfoundland) have conditions of humidity, cloudi- 
ness, and fog similar to those of marine climates on western coasts. 
As a result, the sensible temperatures of summer are high and those 
of winter low. 

In contrast with the eastern coast of North America, much of 
the eastern coast of Asia has such a distinct summer maximum of 
rainfall that its climate might be called a temperate monsoon climate. 
In the winter time, on the contrary, the out-flowing wind from the 
continental interior gives clear, cold, and dry conditions over most of 
the coast. The winter cold is greater than in corresponding latitudes 
in eastern United States, but varies considerably in degree. Places 
on the coast opposite large valleys leading from the interior are 
colder in winter than places lying much farther north, but shielded 
by mountains. Thus Nikolayevsk, Lat. 53 8', near the mouth 
of the Amur River, has a January mean of — 10. i°; and Ayen, Lat. 
56 28', protected by mountains to the west, has a January mean 
of -4.7°. 

Effects on life. The climate of lee coasts in general is so like 
that of humid continental interiors that the conditions of life in the 
two situations are much the same. The chief difference is that tem- 
perature changes of a given amount are felt more near the coast than 
in the interior, because humidity is higher. In the United States, 
the ill effects of variable weather and climate are greatest in the 
coastal sections of the northeastern states. This is shown in the 
greater prevalence of colds and affections of the respiratory organs 
(especially catarrh). 



TYPES OF CLIMATE IN TEMPERATE ZONES 209 

The humid parts of the temperate zone are the great cereal dis- 
tricts of the world. They bear the same relation to the cultivation 
of cereals that the semi-arid steppe lands, with their grassy vegetation, 
bear to the live stock industry of the world. Thus the great wheat 
regions lie mainly between the 40th and 55th parallels. Rye, closely 
related to wheat in its uses and conditions of growth, replaces 
wheat in many localities where the soils are too poor for the latter. 
Of the other great cereal crops in this belt, oats and barley are to the 
north, and corn to the south. Hence, through the heart of the tem- 
perate zone is found the home of all the cereals, save rice, which serve 
as food for man. This arrangement of important crops influences 
both the distribution of population and the movement of commerce. 
The populous part of the temperate zone corresponds closely to the 
cereal belt. Much of the commerce of the world now moves along 
east and west routes in these same latitudes.' No other country is 
situated so well as the United States with respect to cereal-growing 
lands. 

The whole humid section in the interior of this country is in danger 
of sudden frost in late spring and early autumn (Fig. 109), and in 
either case wide-spread damage may result. Its southwestern part 
is exposed to hot winds from the south, which, in exceptional cases, 
wither and kill crops. Droughts are common, though less frequent 
and less wide-spread than in monsoon countries. Almost every year 
some part of the humid portion of the United States suffers from too 
little rain ; but severe drought rarely affects a great area, or the same 
area frequently. In monsoon countries like India, on the other hand, 
a large area suffers from drought at the same time, and the same 
area may suffer for a period of years. Tropical and sub-tropical 
Australia also has frequent and long-continued droughts which affect 
large areas. Hence in spite of its extremes of climate, central and 
eastern United States is a highly prosperous agricultural region, 
largely because of its reliable rainfall. 

The northern limit of the north temperate zone is so far north 
that the summers of interior lands near it are too short and too cold 
for cereals. In the most favorable parts of continental interiors, not 
even the hardiest cereals can be produced much beyond the 60th 
parallel (Fig. 101). Dense forests practically disappear before the 
northern margin of the zone is reached, being replaced by 
the scattered trees and scanty vegetation which mark the beginning 
of the frozen polar wastes. Both Canada and Russia have large 



ELEMENTS OF GEOGRAPHY 






areas of nearly worthless, almost uninhabited, northern territory 
(P- 5°7)- The United States, on the other hand, is neither too 
far north nor too near the equator. Climatically, it has the best 
position of any large country. 

5. MOUNTAIN CLIMATES 

Temperature. Even moderate altitudes so affect temperature 
as to determine what crops may be cultivated. For example, in the 




Fig. 109. Map of United Stales showing average dates of last killing frost 
in spring (broken lines) and first killing frost in autumn (solid lines). (After U. S. 
Weather Bureau.) 

plateau sections of Pennsylvania, in Lat. 40 to 42 , corn cannot 
be depended on to ripen at an altitude of 2,000 feet. In some 
of the drier, hence warmer (in summer) and sunnier, parts of the 
arid West, corn, under irrigation, will ripen at much higher 
altitudes (4,000 feet about Great Salt Lake). In general, the 
upper limit for even the hardiest crops does not exceed 6,000 
feet, even in the lower latitudes of the temperate zone. In 
contrast, corn is grown in Bolivia at an altitude of 10,000 
feet, and wheat even higher. The timber-line (upper limit 
of timber) in the United States ranges from an altitude 






TYPES OF CLIMATE IN TEMPERATE ZONES 211 

of about 11,000 feet at the south, to 7,000 or 8,000 at the north, and 
the level at which snow lies most of the time is not far above these 
limits. Hence, so far as agriculture is concerned, the higher lands of 
the temperate zone are of little use. 

Precipitation. The effect of altitude on rainfall is the same in 
the temperate zone as elsewhere. It increases the amount of precipi- 
tation, and tends in many cases toward a maximum in winter. In 
most places, the increased precipitation at higher altitudes results in 
heavy snowfall (Fig. no) in winter. Thus Baltimore, altitude 104 




Fig. no. Mean annual snowfall in inches, for United States. The snowfall 
on the Sierra Nevada and Rocky mountains is much greater than shown on this 
chart. (After Henry.) 



feet, has an average of 23.8 inches of snow annually, while Grants- 
ville, Md., altitude 3,400 feet, has 71.2 inches. Summit, the top of 
the pass crossed by the Central Pacific railroad, east of Sacramento, 
Cal., has over 400 inches of snow in a year, and nearly 300 inches 
have been recorded in a single month. Sacramento, on low land to 
the west, has only a trace of snow each year. 

Winter snowfall (Fig. no) is an important factor in the flow of 
many rivers. Water from rapidly' melting snow may cause winter 
and spring floods in some cases, and in other cases the gradual 
melting of snow aids in (1) the development of water power, 



212 ELEMENTS OF GEOGRAPHY 

(2) the maintenance of a sufficient depth of water for navigation, and 

(3) irrigation. Heavy winter snows and snowslides offer serious 
problems to railroad lines which run at high levels, and at the bases 
of mountains. Snowslides are one of the things to be feared about 
mines in mountains, and they are in some cases destructive to moun- 
tain villages. 

Mountain conditions of temperature and rainfall favor forests, 
and make many mountains the sites of lumbering (p. 480). Forest 
trees thrive far above the altitudes which limit crops. Different 
species of trees prevail at different altitudes, and with different amounts 
of rainfall. Thus in Pennsylvania, a large variety of forest trees is 
found, with a resulting wealth of forest resources, in a relatively 
small area. Even in many arid regions, lands 5,000 to 6,000 feet 
high have rain enough to support forests of commercial value. 

Many mountains serve as health resorts as well as pleasure resorts 
(p. 482). In most cases the mountain health resort is related to the 
treatment of diseases of the lungs, especially tuberculosis. Mountain 
climate is not a cure for tuberculosis; but the conditions afforded by 
the climate of the mountains may aid in checking the disease, or may 
even enable the organs affected to throw it off. The favorable condi- 
tions are (1) the pure, dry air characteristic of the higher altitudes, 
and (2) the decreased density of the atmosphere, which stimulates 
the lungs to greater activity. In the arid parts of western United 
States especially, these conditions are associated with bright, sunny 
weather (Fig. 50), which favors out-of-door life. 

Questions 

1. Suggest various ways in which temperatures and changes of tempera- 
ture during a year affect people and their occupations. 

2. Explain the absence of summer rainfall in sub-tropical climates, even with 
winds from the ocean. 

3. Account for the daily morning fogs of the coast of southern California in 
summer. 

4. Explain fully the differences of climate between the coastal and interior 
stations in California (Tables I and II). Suggest probable effects of these dif- 
ferences on man and his occupations. 

5. Discuss the influence of the Gulf of Mexico on the climate in southeastern 
United States during summer. During winter. 

6. Give the reasons for the differences in climate between the stations in 
Table IV. State some effects of these contrasts on the life of the region. 

7. How would you expect the distribution of population in Chile to be affected 
by climate (p. 194)? 



TYPES OF CLIMATE IN TEMPERATE ZONES 213 

8. Why is the Pacific Ocean not the chief source of moisture for the United 
States? 

9. Explain the differences in climatic conditions along the 41st parallel in the 
United States. Along the 32d parallel. 

10. What would be the commercial effects, if the ports as far south as New 
York were ice-bound for two months in winter? 

11. Why are there few summer resorts on the Atlantic coast south of Dela- 
ware Bay? 

12. What would be the probable effects on the climate of the United States 
if a mountain range stood along the Canadian boundary line? 

13. Explain the increase in rainfall from San Diego northward to Astoria. 

14. Why is the limit of cereals and of permanent habitations nearer the 
equator in the areas shown by Fig. 100 than in the areas shown by Fig. 101? 

15. How does the course of the isotherm of 50 in Fig. 100 differ from that 
of the same isotherm in Fig. 101? Why? 

16. Suggest reasons, based on Figs. 100 and 104, why there is little commerce 
between lands of the South Temperate Zone. 

17. Why should the northeast coast of the United States have more rainfall 
in winter than in summer? See Figs. 103 and 107. 

i'8. Why do the lines showing average dates of frost (Fig. 109) turn northward 
over Lake Erie and along the south Atlantic coast? 

19. Why is the snowfall in the Mississippi Valley heavier than that in the 
corresponding latitudes on the Atlantic coast? 



References 

Abbe: A First Report on the Relations between Climate and Crops; Bull. No. 36, 
U. S. Weather Bureau. 

Brown, R. M.: Climatic Factors in Railroad Construction and Operation, in 
Jour. Geog., Vol. Ill, pp. 178-190. 

Chamberlain: Climatic Conditions in Southern California, in Jour. Geog., 
Vol. I, pp. 297-302. 

Fenneman: The Climate of the Great Plains, in Jour. Sch. Geog., Vol. Ill, 
pp. 1-4, 46-53- 

Henry: Climatology of the United States; Bull. Q, U. S. Weather Bureau. 

Huntington: The Pulse of Asia. (Boston, 1907.) 

Platt: Climatic Control in the Desert, in Jour. Sch. Geog., Vol. IV, pp. 255- 
'263, 281-286. 

Russell: North America, Ch. III. (New York, 1904.) 

Semple: Influences of Geographic Environment, Ch. XVII. (New York, 1911.) 

Stupart: The Climate of Canada, in Scot. Geog. Mag., Vol. XIV, pp. 73-80. 

Ward: Climatic Control of Occupations in Chile, in Jour. Sch. Geog., Vol. I, 
pp. 289-292. 

Ward: Climate, Chs. V, IX. (New York, 1908.) 

Ward: Climate in Some of its Relations to Man, in Pop. Sci. Mo., Vol. LXXVI, 
pp. 246-268. 

Watt: The Climate of the British Isles, in Scot. Geog. Mag., Vol. XXIV, pp- 
169-186. 



CHAPTER XI 
CLIMATE OF POLAR REGIONS 

General Considerations 

Extent of polar regions. The limits of the polar regions are 
commonly placed at the Arctic and Antarctic circles; but they are 
sometimes regarded as being limited equatorward by the isotherm of 
50 for the warmest month, an isotherm which marks the approxi- 
mate limit of the growth of trees and cereals (Fig. in). This 
isotherm lies south of the Arctic Circle in most of North America 
and Asia, but north of it along windward coasts, as in Alaska and 
Norway. In this discussion, the latitude division is used for the 
sake of simplicity. Such a division gives the polar regions an area 
about one-twelfth that of the earth. 

Land and water areas. The distribution of land and water in 
the polar regions of the northern hemisphere is nearly the reverse 
of that in the southern hemisphere. All the continents of the former 
extend north of the Arctic Circle (Fig. in), and to the continental 
lands must be added part of Greenland, and various smaller islands. 
The ratio of land to water is about 2 to 3. The total extent of land 
is small, compared with that of other zones, but a wrong notion of 
its extent is common, because of the use of the Mercator map 
(p. 25), which exaggerates areas in high latitudes. The only large 
land area in the south polar region is Antarctica, most of which is 
covered with snow and ice (p. 218). 

General features of polar climate. All polar regions are alike 
in having the sun above the horizon for more than twenty-four con- 
secutive hours, and below the horizon for a similar period, once 
each year. Near the equatorward margins of these zones, the longest 
period of continuous sun is but a few days (of 24 hours each) ; but the 
time during which the sun does not set increases poleward until, at the 
poles, the day (period of continuous light) is six months long (p. 20). 
During the period of continuous light, insolation is greater in polar 
regions than in low latitudes (p. 57), but the temperature of the air 

214 






CLIMATE OF POLAR REGIONS 



215 



is not raised accordingly, because (1) the sun's rays are very oblique 
(Fig. 35), and (2) much of the heat which reaches the surface melts 
ice and snow, and is not effective in warming the air. The result is a 




Fig. in. Map of North Polar Zone, showing land and water areas. Pole- 
ward limit of growth of cereals Poleward limit of growth of forest trees 

. Poleward limit of permanent habitations + + + + +. Isotherm of 50 for 

warmest month . 

low temperature for the year, and, except for lands free from snow and 
ice, a low temperature at all times of the year (Fig. 112). 

Our knowledge of the climate of polar regions is rather fragment- 
ary. The known data are from scattered localities, and are mainly 
the records of observations of different exploring expeditions. More 



216 ELEMENTS OF GEOGRAPHY 

data are available for the north polar region than for the south. 
Conditions near the margin of the former are known fairly well, but 
in the higher latitudes, observations covering long periods of time have 
not been made. 

Temperature. The winters are always cold and, as noted, the 
average temperatures for the year are always low (Fig. 40). 
Many of the recorded temperatures of January in the Arctic region 
range from — 40 to — 6o°. The summers are cool, or even cold. 
The warmest month has an average .temperature of 32 or more in 
many places, and the maximum summer temperatures close to the 
margin of the zone are locally as high as 8o°, or even 90 (Fig. 112). 
Such temperatures occur only where there are large areas of land free 
from snow and ice. Most of the Antarctic region has a summer 
temperature below the freezing point even for the warmest month,, 
so far as present records show. 

The annual range of temperature in the Arctic region is greater 
than that in the Antarctic, because more land in the former is not 
covered by snow and ice in summer. In Eurasia, for example, the 
great area of land near the Arctic Circle, free from snow and ice in 
summer, becomes warm, but the winter temperatures are the lowest 
known. Verhoyansk, in Siberia, just within the Arctic Circle (Lat. 
67 6'), has a July mean of +6o° and a January mean of — 6o°. In 
contrast with this continental locality, Hammerfest (Lat. 70 40'), 
on the coast of Norway, and the most northerly town in Europe, 
has a January mean of 23 , and a July mean of 53 . The latter 
station shows the full effect of the ocean on the temperature of 
windward coasts in high latitudes. At Hammerfest, the sun does 
not set from the middle of May to the end of July. 

Humidity and precipitation. The low temperatures affect the 
other elements of climate. They mean little evaporation, and hence 
little moisture in the air; but the relative humidity varies from 
extremely low, especially far from the sea to windward, to relatively 
high, particularly on windward coasts. The precipitation is light, 
probably averaging less than 15 inches a year except on windward 
coasts. 

The Shackleton expedition to Antarctica found, from recording instruments 
left by a preceding expedition (Capt. Scott, the "Discovery"), that the average 
precipitation for six years had been the equivalent of 7 to 8 inches of rain. Most 
of the precipitation in polar regions is in the form of snow, and is frequently 
accompanied by violent winds. Rain is said to fall in most parts of the north 






CLIMATE OF POLAR REGldNS 



217 



polar region during the warmer months. In the south polar region, on the 
contrary, the Shackleton expedition found all precipitation during 13 months to 
be in the form of snow. 

The great fields of snow and ice in the polar regions are not due 
to heavy snow-fall, but to the preservation of most of that which 




Fig. 112. Map of North Polar Zone, showing mean annual isotherms (- 
isotherms for January ( ), and for July ( ). 



falls. It melts and evaporates little. Instead of being made up of 
distinct flakes, it is usually in the form of tiny ice spicules, which 
readily become compact, and make a hard, solicl mass almost like 
ice. It is said that this difference in the character of the snow 
explains the ease with which the Eskimo makes his snow hut. 



218 ELEMENTS OF GEOGRAPHY 

The small amount of moisture in the air suggests little cloudiness. 
Few records on this point are available, but in summer, fogs about the 
ice-covered lands and seas are common, and are a great hindrance to 
navigators. Interiors are probably less foggy, and the winters are 
likely to be clear (Why?). 

The northern and southern polar regions are so unlike, with respect 
to the distribution of land and water, that they may be considered 
separately, so far as further details of climate and their results are 
concerned. 

The Antarctic Region 

The Antarctic region is essentially one of ice-covered water and 
ice-covered land. South America, which extends farther south than 
Africa and Australia (Fig. ioo), lacks more than 700 miles of reaching 
the polar circle. The known land within the Antarctic Circle con- 
sists of scattered areas such as Graham Land, Coats Land, and South 
Victoria Land, discovered by various expeditions. It is believed 
by many that these scattered land areas are parts of the border of an 
Antarctic continent. Most of the region lies under a cover of snow 
and ice of great thickness, which meets the sea in many places, with 
no sign of land beneath it. This "Great Ice Barrier," as it is called, 
is a cliff of ice 30 to 300 or more feet in height, extending for a known 
distance of hundreds of miles. Beyond it, the elevation of the surface 
increases toward the interior to heights of several thousand feet. 
The major part of the Antarctic region may be described as an ice 
plateau, though high mountains nearly free from ice project through 
it in places. 

Summer temperature. The isotherm of 50 for the warmest 
month crosses southern South America (Fig. 100). If the south 
polar region were limited by this isotherm, it would include every- 
thing south of the 55th parallel. The great expanses of ice and 
ice-water do not allow the temperature of this zone to rise much 
above 32 , even in summer. During the summer, fog and cloud 
are reported as being so frequent that much insolation is cut off. 
Fogs and clouds are therefore important factors in keeping the summer 
temperatures low. 

Winter temperature. The mid-winter (July) temperatures of 
the lower latitudes' of this zone are about — 15 to — 20 , so far as 
recorded. The temperatures of higher latitudes are probably much 
lower. The real character of the winter may perhaps be shown better 



CLIMATE OF POLAR REGIONS 219 

by the fact that the Shackleton expedition recorded a winter minimum 
of — 57 , and the report of the voyage of the "Discovery" shows a 
minimum of — 67 . 

The seasons between winter and summer are very short. The 
one shows a rapid rise from the low temperatures of winter, and the 
other a rapid drop from the temperatures of summer. 

Effects on life. The effect of these temperatures on life is 
marked. The Antarctic region is devoid of most kinds of vegetation 
familiar to us. Some mosses and lichens are found on such lands as 
are free from ice for a part of the year, but no form of vegetation use- 
ful to man is known. 

The animal life is mainly marine, whales and seals being character- 
istic species. The waters abound in lower forms of life, such as 
molluscs and still simpler types. The only varieties of animal life 
on the land are a few birds and insects. For the former, the Cape 
Adare region (Victoria Land, south of New Zealand) is perhaps the 
chief locality. Here, in latitude 71 S., the great rookeries of penguins 
constitute one of the most remarkable assemblages of bird life to be 
found anywhere in the world. In addition to the penguin, the 
albatross, gull, and some other varieties of sea-coast birds are found. 
From the standpoint of life in general, however, the Antarctic lands 
are as close an approach as there is to an absolute desert. 

The Arctic Regions 

Parts of Alaska, Canada, Scandinavia, Russia, and Siberia, and 
a number of large islands are in the north polar zone (Fig. in). 
The lands here are in the lower latitudes of the zone, not in the higher, 
as in the southern hemisphere. 

A part of the Arctic region is like most of the Antarctic in being 
covered with snow and ice all the time, but a larger part is not so 
covered. In the higher latitudes of the zone, the Arctic Ocean is 
covered with ice most of the year, though it is more or less broken in 
the summer. In the lower latitudes of the zone, much of the ocean 
is free from ice all or part of the time. In addition to the ice on the 
ocean, snow and ice cover all but the fringe of Greenland, and the 
larger part of many other islands. In Greenland, the snow and the 
ice developed from it have reached such a depth as to conceal all 
inequalities of surface beneath (p. 385). 

The Arctic portions of the continents are not covered by ice 



220 ELEMENTS OF GEOGRAPHY 

and snow during the summer, and their climate is in sharp contrast 
(How?) with that of regions which are so covered. There, is also a 
contrast between the interior lands which are snow-free during the 
summer, and windward coasts, such as western Alaska and north- 
western Norway, which are affected by the moderating influence of 
winds from the oceans. 

Temperature. The temperatures of the Arctic zone vary widely. 
The lowest yearly temperatures are found where there is a permanent 
covering of ice. The interior of the ice-cap of Greenland is supposed 
to have an annual mean close to zero, and an average below 32 for 
the warmest month of the year. Its temperatures are probably 
similar to those close to the pole. 

The winter conditions in Arctic regions are better known than are 
those in the Antarctic, because more expeditions have gone north. 
Such observations as are recorded indicate a January mean of about 
— 40 for northern Greenland, giving it an average annual range of 
about 70 . The continental interior of Siberia is even colder than 
Greenland in winter (Fig. 112). The region about Verhoyansk (p. 216) 
has the lowest average mid-winter temperatures recorded ( — 50 to 
— 6o°), and is known as the "cold pole of the earth." In summer, 
however, this same region, being without snow or ice, becomes very 
much warmer than Greenland. The annual range of temperature 
in Siberia (120 ) is, therefore, greater than that in Greenland, while 
the mean temperature for the year is about the same. 

The Arctic islands near North America have a temperature simi- 
lar to that of Greenland. Northwestern Canada and Alaska, even 
back from the coast, are somewhat warmer. At Ft. Yukon, Alaska, 
Lat. 66° 34', the average for the winter months is about — 24 , and 
for summer months, 57 . 

Arctic lands free from snow in summer have great extremes of 
temperature, beyond the average annual range. The average 
minima of winter are commonly as low as — 70 , and Verhoyansk 
has reported — 94 F., the lowest natural temperature ever recorded. 
Summer maxima of 6o° to 8o° are almost typical of the margin of 
the zone, and average maxima of 6o° are not uncommon as far 
north as latitude 8o°. Temperatures of 90 or more are frequently 
reported from Alaska and Siberia. An extreme range of 150 for 
the year is common, and the highest summer and lowest winter tem- 
peratures recorded are more than 180 apart. 

The extreme and long-continued cold of winter is sufficient to 



CLIMATE OF POLAR REGIONS 221 

freeze the water in the ground to the depth of scores of feet. The high 
temperatures of summer suffice only to melt the ice in the top part of 
the soil. The rapidity with which the Arctic summer comes on, and 
the brief period of warmth, are indicated by conditions in the interior 
of Canada near the margin of the zone. Both April and October have 
mean temperatures ranging from io° to 15 below the freezing point. 
The May and September mean temperatures are below 40 , a figure 
which implies freezing temperatures every night. June, July, and 
August are warm, with mean temperatures above 50 (near 6o° for 
July). In higher latitudes the monthly means are lower, and the 
warm season is correspondingly shorter, until there is practically no 
summer at all. 

Plant life. The relatively high temperatures which prevail on 
ice-free land in summer permit the growth of many kinds of plants. 
The only Arctic lands without green plants are those permanently 
covered with ice and snow. As compared with the temperate zone, 
however, the amount and variety of vegetation are meager. 

The southern margins of polar lands support stunted trees of 
the hardier types, such as larches, pines, birches, and willows (Fig. 
in). The average northern limit of these trees is near the 70th 
parallel in Siberia and northwestern Canada, and their extreme 
limit about latitude 72 , along some of the sheltered river bottoms in 
north central Siberia. Dwarf willows and birches (hardly trees) are 
said to occur 8° or io° farther north. The limiting factors appear to 
be wind and evaporation, rather than the low temperatures of winter 
or the short growing season. 

Many varieties of herbaceous plants thrive. Their character 
and their occurrence are related closely in many cases to topography. 
On level areas, the soil becomes a sea of mud as it thaws out during 
the summer. Mosses, lichens, and other low types of plants, are 
most abundant in the Arctic tundra — desolate, monotonous, and 
almost worthless. 

Where more favorable conditions exist, as in the dry places in 
the tundra, or on southerly slopes where there are both drainage of 
the soil and greater insolation, there are large numbers of flowering 
plants, some of which produce berries. On the west coast of Green- 
land, poppies are found north at least to latitude 78 . The plants of 
these high latitudes are for the most part rapid growers, as the short 
growing season would let no other plants mature. They have short 
roots, for all but the upper surface of the soil is frozen. 



222 ELEMENTS OF GEOGRAPHY 

The temperatures of air and soil virtually exclude crops from the 
polar region. There are only a few favored localities where the 
hardier types of cereals may be grown (Fig. in). Thus in northern 
Norway, under the influence of the sea, some crops, notably barley, 
are grown within the Arctic Circle. Small areas in favored situations 
in Alaska and Siberia permit the growth of the hardiest crops, but in 
most of the Arctic region agriculture is out of the question. The ice- 
cold waters of the Arctic regions abound in sea-weeds. 

Animal life. Animal life, as well as plant life, is more abundant 
in the Arctic regions than in the Antarctic. This follows from the 
greater extent of land, the more favorable temperatures of summer, 
and the greater amount of vegetation. Sea life is more abundant than 
land life. The larger sea animals are similar to those of the Antarctic, 
and include species of whales, seals, and walruses. All these types 
bear an important relation not only to the life of the inhabitants of 
the Arctic region, but also to certain industries carried on from places 
in lower latitudes. Thus, sealing and whale fishing are carried on 
close to the Arctic Circle, and even within it. The Arctic seas also 
teem with smaller forms of life. Thus molluscs and small crustaceans 
abound on the coast of north Greenland, at least as far north as 
latitude 78 . 

Among land species, birds are prominent in the summer. The 
little auk, dovekies, guillemots, and (locally) the eider duck 
abound. Among land mammals, the reindeer, fox, hare, polar bear, 
and musk ox may be mentioned. 

The effect on population. The Arctic region, unlike the Ant- 
arctic, is inhabited by human beings (Fig. in). The population, 
however, is scanty, scattered, and, on the whole, not highly civilized. 
Along the southern margin of the zone, there are many small groups 
of people. Farther north, the groups are fewer and smaller, and 
more confined to coasts. The most northerly permanent settlements 
are on the west coast of Greenland, the northernmost, Etah, being 
above the 78th parallel. 

For all inhabitants of polar regions, life is a constant struggle. 
This is in great contrast with the situation in the tropics. In the 
latter region, the monotonous heat throughout the year means a 
great bounty from nature, unfailing ease of existence, and consequent 
lack of incentive to work and progress. The cold of the polar regions 
means poverty of resources, a constant fight for food and clothing, 
and consequent inability to progress. In the temperate zone, winter 



CLIMATE OF POLAR REGIONS 223 

imposes difficulties somewhat like those encountered in the north, 
but winter alternates with summer, the season of plenty. 

The natives of polar regions depend on animal life. Edible 
plants are absent, except in the lower latitudes of the zone, and for 
a short time each year. Land animals, like the reindeer, are com- 
paratively scarce on account of the meager vegetation. Hence the 
people depend in large part on marine life, and most of them live 
along the coasts. 

Food is furnished by the seal, the walrus, and fish, supplemented 
by the reindeer, the hare, the bear, and birds. Most of this food 
can be obtained only during the time of light, which is therefore the 
hunting season. Food for winter is preserved easily because of the 
cold. As the latitude increases, the number of days when there is 
no light also increases; hence, the amount of provision which has to 
be made against the dark season is greater, and the number of days 
favorable for hunting is correspondingly less. These factors, as well 
as climate, tend to limit the settlements to the lower latitudes. The 
dependence of the people on animal life makes them hunters and 
fishers. The hunters are usually nomadic, going about in search of 
game during the summer, but having fixed habitations for winter. 
The natives who iive chiefly by fishing are likely to have permanent 
settlements, especially if the supply of fish is abundant. 

The principal food of the Eskimo is meat, in contrast with that 
of the tropical native, who lives chiefly on fruit and vegetables. The 
two types of diet correspond, in a way, to the needs of man in cold 
and hot countries. The meat produces more fat and more heat. 
Since fuel and means of cooking are meager, much meat is eaten raw. 
If cooked at all, it is in the most primitive way. In north Greenland, 
the tiny fire — a little oil with a wisp of grass or moss for a wick — is 
used chiefly for melting snow and ice for drinking water. 

The dependence of the Eskimo on animal life is shown again in 
the materials which he uses for his clothing and for his tents. Most 
of his clothing is of fur. Plant fibers which could be woven or braided 
together are unknown. The fashioning of garments from furs and 
skins is comparatively simple. The materials used in making dwell- 
ings depend on local circumstances. Where forests are accessible, 
as along the margin of the zone, or where driftwood can be had from 
the ocean, as along some coasts, wood is used. Elsewhere, the winter 
habitation is usually of stone or snow, particularly in the case of 
hunting tribes. During the hunting season, the hunters live in 



224 ELEMENTS OF GEOGRAPHY 

tents of skins. In the winter, they settle down in communities, living 
in stone or snow huts. 

The conditions of the Arctic regions exert a considerable influence 
over practically all details of the life of the people. In summer, 
travel over large areas of the tundra is almost impossible on 
account of the mud. In winter, on the contrary, when the ground is 
frozen and covered with snow, travel by sledge is easy. Weapons and 
utensils may be made from wood, if it is available; more commonly 
they are made from bone and hides. The use of these animal pro- 
ducts is the characteristic feature of the arts and crafts of the Eskimos. 
Perhaps in no other thing is their skill shown better than in the manu- 
facture of their kayaks (boats), where the only materials to be had 
are bone, pieces of driftwood, and hides. Out of these they fashion 
a craft wonderfully adapted to the uses to which it is put. 

Looked at with reference to their surroundings, the Eskimos 
hardly can be regarded as backward. Probably they make better 
use of the things at their command than more highly civilized men 
could, but Arctic climate is too great a handicap to allow them to 
progress far. 

Questions 

i. Why is rainfall relatively unimportant in affecting the distribution of 
people in the polar regions? 

2. If the entrance from the Pacific to the Arctic Ocean were widened greatly, 
what would be the probable effect on the climate of polar North America? 

3. Suggest reasons why the Antarctic has been less well explored than the 
Arctic regions. 

4. Do the reasons given in answer to the preceding question help to explain 
the absence of plants and land animals from the Antarctic land areas? 

5. Why do trees grow in higher latitudes in Asia than in North America 
(Fig. in)? 

6. What factors determine the courses of the isotherms for January in Fig. 
112? How? 

7. Why are the courses of the isotherms for July different from those for 
January in Fig. 112? 

8. How are the soil conditions of Arctic regions harmful to crops? 

9. Why is there an ice-cap over central Greenland and not over lands in 
the same latitude in northern Asia? 

References 

Abbe: The Climate of Alaska, in Prof. Paper No. 45, U. S. Geol. Surv., pp. 
i33-!48. 

Gibbs: Transportation Methods in Alaska, in Nat. Geog. Mag., Vol. XVII, 
pp. 69-81. 



CLIMATE OF POLAR REGIONS 225 

Grosvenor: Reindeer in Alaska, in Nat. Geog. Mag., Vol. XIV, pp. 127-148. 

Mossman: The Greenland Sea: Its Summer Climate and Ice Distribution, 
in Scot. Geog. Mag., Vol. XXV, pp. 281-310. 

Peary: Northward Over the Great Ice, Vol. I, Ch. XVI. (New York, 18.98.) 

Shackleton: The Heart of the Antarctic, Vol. II, Appendices I, V. (Phila- 
delphia, 1909.) 

Ward: Climate, Chs. VI, X. (New York, 1908.) 



CHAPTER XII 



THE OCEANS 



General Considerations 



Importance of the oceans. The oceans are of great importance 
to the rest of the earth in many ways, some of which have been 
pointed out. Thus the distribution of temperatures, humidity, 
rainfall, and cloudiness are related closely to the oceans. Waves 
and currents are constantly wearing away the land in some places 
and building new land elsewhere. On the whole, destruction exceeds 
building, so far as land is concerned; consequently, the ocean tends to 
extend its area at the expense of the land (p. 522). 

The ocean is an important source of food, and furnishes large 
amounts of other useful materials. Thousands of people are em- 
ployed in getting commercial products from the ocean. Other thou- 
sands are engaged in the carrying trade over the oceans. Formerly 
the oceans were barriers to travel and communication, but swift steam- 
ships and cable lines (Fig. 113) now make communication between 
the continents easy. Nine-tenths of our foreign trade is carried by 
vessels (Figs. 114 and 115), most of which hail from other countries. 
Enormous quantities of goods are shipped annually to the United 
States from all the leading countries of the world and from the 
United States to these countries (Figs. 116 and 117), over the ocean 
highway. The voyage across the Atlantic formerly took as many 
weeks as it now takes days, while the happenings of this morning in 
Europe may be printed in the evening papers of Buenos Aires. 

The ocean basins. The oceans lie in the great depressions in 
the surface of the lithosphere (p. 33). Fig. 118 suggests the real shape 
of an ocean basin, which is, in general, convex upward. The surface 
of the water in these basins is even, and is usually spoken of as level. 
In reality it is a curved surface, with its curvature nearly that of a 
sphere. 

The oceans are more extensive in the southern hemisphere than 
in the northern. They encircle the earth in latitude 6o° S. (Fig. 

226 



THE OCEANS 



227 




a 


Tt 


a 


~! 


en 

4-J 


O 
U 






O 


-1 


a 


IH 


r£ 


rt 



a, td 



228 



ELEMENTS OF GEOGRAPHY 



113), and the waters south of 40 S. are sometimes called the Southern 
Ocean. From it the Atlantic, Pacific, and Indian oceans extend 
northward thousands of miles. In the northern hemisphere the 
land makes an almost complete circuit in latitude 6o° to 70 (Fig. 
113), whence it extends southward in two great arms. North of 
latitude about 70 lies the Arctic Ocean, almost surrounded by land 




Fig. 114. Diagram showing movement of exports from the United States by 
kinds of conveyances (1910). 




Fig. 115. Diagram showing movement of imports to the United States by 
kinds of conveyances (1910). (Of 4,501 vessels horn foreign ports arriving at New 
York City in 191 1, only n were sailing ships.) 

(Fig. in) and therefore with but narrow connections with the larger 
oceans. The area of the different oceans (according to Ravenstein) 
is about as follows: 

Arctic Ocean 5,200,000 square miles 

Indian Ocean 28,000,000 square miles 

Atlantic Ocean 35,000,000 square miles 

Pacific Ocean 67,000,000 square miles 

Southern Ocean 5,700,000 square miles. 

The volume of water in the oceans is nearly fifteen times the vol- 
ume of the lands. If all the material of the land were deposited in 
the sea, it would raise the level of the water about 650 feet. 



J 



THE OCEANS 



229 





Un.King. $ 550 S9.5 - 
Germy 258 13.8* 
France lis 6.2* 
Nether. 84 45* 
Italy 52 2B* 
Other 120 T.t+ 

it : 



Austral. *3l 16* 

Japan 26 1.4* 

Phil.Is. .19 1.0* 

China 15 OS* 
India 7 

Other 23 13* 



Argent *427 23* 

Brazil 24.9 13* 

Chile 9.9 0.5* 

Other 22.5 12* 



Br.S.APr. *11.4 Ote* 
PortAfr. 3.4 0.2* 
Br.WAfr. 8.3 
Egypt 13 
Other 25 



XT' 




j 



Fig. 116. Diagram showing destinations of exports from the United States 
by continents and leading countries (1910). (Values in millions of dollars; per- 
centages are proportions of total exports.) 




Brazil $103 


6.6'' 


Argent 32 


2.1*' 


Chile 20 


13''" 


Other 33 


2.2 i 



Fig. 117. Diagram showing sources of imports to the United States by con- 
tinents and leading countries (iqio). (Values in millions of dollars; percentages 
are proportions of total imports.) 



ELEMENTS OF GEOGRAPHY 





Exploration of the ocean. The motions of the 
surface of the ocean, such as waves and tides, may 
be observed from the shore, but it has taken the 
work of many exploring expeditions to give us our 
present knowledge of the depths of the ocean and 
the conditions of its bottom. 

The depth of the ocean is known by soundings, 
which are made from ships by reeling out a heavy 
weight held by a fine steel wire (Fig. 119). The 
weight is so fastened to the line as to be set free 
when it reaches the bottom, for this is simpler than 
to draw it up again. A sounding of 3,000 fathoms 
(a fathom = 6 feet) can be made in about an hour. 
A series of soundings in any region give a fairly accu- 
rate idea of the form of that part of the sea-floor. 

The sediment on the bottom of the sea may be 
brought to the surface by various sorts of appa- 
ratus. The cup lead, a common form used, is 
shown in Fig. 120. B is a hollow, inverted cone. 
Above the cone is a sliding disc, D, a little larger 
than the base of the cone. When this apparatus 
is let down, the cone sinks into the soft sediment 
and is filled with it. On being raised, the disc 
shuts down on the cup and holds its contents in. 
Another device, known as a water-bottle, is used to 
secure samples of water from various depths, while 
a self registering thermometer records the tempera- 
tures at different levels. Hence a single sounding 
may give the depth, a sample of the sediment 
on the bottom, samples of the water, and a record 
of the temperature. 

Larger samples of material from the bottom 
and . specimens of deep-sea life are obtained by 
dredges (Fig. 121). When the dredge is let down, 
the strip of metal, E, drags along the bottom, and 
turns the sediment into the sack. Swabs are at- 
tached below to entangle small animals missed by 
the dredge. 

Materials of the bottom. From sounding and 
dredging it is known that most of the sea-bottom 






THE OCEANS 



231 



is covered with soft sediment, which has come from many sources. 
Some of it was carried to the sea by rivers, some was worn from 
the shores by waves, some was blown from the land, some is made 
up of the shells and skeletons of organisms which lived in the water, 
and some consists of fine debris thrown out from volcanoes beneath 




Fig. 119. Fig. 120. 

The sounding line. The cup lead. 



Fig. 121. 
The deep-sea dredge. 



the sea. A little cosmic ("shooting-star") dust is also present. 
Near many shores, gravel and sand derived from the land cover the 
bottom. Little gravel is found in depths of more than a few 
fathoms, though gravel and bowlders carried out by icebergs are 
found occasionally at great depths far from land. Sand, too, is found 
chiefly in shallow water, but extends out to depths greater than 
those reached by most gravel. 



232 ELEMENTS OF GEOGRAPHY 

Beyond the narrow belt of gravel and sand along coasts, fine 
sediments, such as mud and clay, prevail; but sediments of organic 
origin are found in many places. Thus coral reefs and calcareous 
mud, the latter made by the grinding up of coral by waves, are found 
in shallow water in many places in low latitudes. Ooze is the name 
applied to those soft materials of the sea-bottom composed largely 
of the shells and other hard secretions of tiny organisms which live 
in the water. Many of the latter live near the surface of the water, 
and their shells and other hard parts sink when the organisms die. 
Oozes are named from the animals and plants which contribute most 
to them. Thus foraminiferal ooze is the ooze in which shells of tiny 
animals called foraminifera are abundant. These shells are mainly 
lime carbonate and enter largely into the composition of chalk deposits 
like those of the English coast and some of the states west of the 
Mississippi River. Chalk deposits, made in ancient seas, are used in 
making whitewash, Portland cement, whiting, and blackboard cray- 
ons. Since these chalk-beds were made, the sea-bottom where they 
were laid down has become land. 

In diatom ooze the skeletons- of minute plants {diatoms) abound. 
It is composed mainly of silica. Some deposits of it, known as 
diatomaceous or infusorial earth, are used as a polishing powder. 
Its porous nature has led recently to its use in making dynamite, 
and for packing pipes and boilers where a non-conductor of heat is 
wanted. Large beds of infusorial earth (some of them perhaps of 
fresh-water origin) are worked in this country, especially in Cali- 
fornia. 

Below the depth of about 2,200 fathoms, the ocean-bottom is 
covered with red clay, the particles of which came from many sources. 
Most of it consists of the decomposed products of (1) materials 
thrown out from volcanoes, (2) dust blown from the land, (3) shells 
and other secretions of marine life, and (4) meteors. 

The sediments of the sea-bottom are to be regarded as rock in the 
making, for they may become solid rock by being cemented together 
(p. 259). This process is taking place at many points in the sea. 
Locally, it goes on as fast as the sediments gather. On the lands 
there are various kinds of rock (conglomerate, sandstone, shale, 
limestone, p. 259), composed of sediments such as are now being de- 
posited in the shallow parts of the sea, but no known formation in the 
land corresponds to the red clay of the very deep sea. This suggests 
(1) that most lands have been, at some time, beneath the sea, and 



THE OCEANS 233 

(2) that, so far as now known, no part of the present continents was 
ever at the bottom of the deep ocean. 

Depth and pressure. The average depth of the ocean (Fig. 
122) is about two and one-half miles, or nearly 13,000 feet. The 
depth exceeds four miles in many places, and the area of very deep 
water is much greater than that of very high land. The areas which 
are far below the average depth of the ocean are known as deeps. 
The greatest depth of water known, 31,614 feet, is in the northern 
Pacific, near the Ladrone Islands. This depth is more than the 
height of the highest mountain (Mt. Everest, 29,002 feet) above the 
sea. There are other areas exceeding five miles in depth in the 
Pacific, which is the deepest ocean. The greatest depth of water 
known in the Atlantic is Blake Deep (27,366 feet), north of Porto 
Rico. This deep, like those of the Pacific, is long and narrow, has 
steep slopes, and is parallel to the great ridge of which Porto Rico 
is a part. In few other places in the Atlantic does the depth reach 
20,000 feet. The Indian Ocean is not known to have depths much 
exceeding 20,000 feet, and the deepest known places in the Arctic 
Ocean and in the Southern Ocean are still less. 

The pressure at the bottom of the deep oceans is very great. 
At a depth of one mile, it is one ton to the square inch, while in the 
greatest deeps it exceeds six tons to the inch. This pressure would 
crush some kinds of stone. Yet the ocean water does not become 
much denser (is not compressed much) even under so great pressure. 
Objects such as pebbles, which sink readily at the surface, sink readily 
to the bottom. The pressure at great depths is an important factor 
in submarine work by divers, since the pressure of air within the 
diver's suit must be about equal to that of the water outside. 

Topography of the bottom. Most of the sea-bottom is nearly 
flat, and therefore very unlike the land. The surface of the land 
is made rough in various ways, especially by running water and 
winds; and the difference between the topography of the land and 
that of the sea-bottom is due largely to the fact that these agents 
do not affect the latter. 

In spite of the general flatness of the sea-bottom, it has many 
irregularities, for there are (1) volcanic cones, some of them built 
up from the bottom of the deep sea to elevations far above its surface 
(p. 302); (2) steep slopes, such as those (a) between the continental 
platforms and the deep sea basins and (b) about some of the deeps; 

(3) valley-like depressions, especially on the continental shelves; 



234 



ELEMENTS OF GEOGRAPHY 




< 



u 



THE OCEANS 235 

(4) great ridges somewhat like the mountain ridges of the land; and 

(5) broad, plateau-like swells. 

(1) Volcanic cones are most numerous in the Pacific Ocean, and 
more numerous in its deeper western part than in its shallower eastern 
part. They seem to rise abruptly, but their slopes are much less 
steep than they seem. The upper parts of few volcanic islands have 
a slope of more than 30 , and the lower parts of most of them slope 
less than 6°. Below the sea, the slope in most cases is less than 3 , 
or 1 mile in 20. 

(2) The slopes around the deeps and at the edges of the conti- 
nental shelves are steep, as slopes in the ocean-bottom go, but much 
less steep than many slopes on land. Submarine slopes as great as 1 
mile in 8 are rare, and 1 mile in 20 not very common. The latter 
slope would make a steep railway grade. 

(3) On many continental shelves there are valleys which are much 
like river valleys. Many of them are continuations of valleys on 
land. Thus the Hudson, Delaware, Susquehanna, St. Lawrence, and 
other valleys are continued out under the sea. Such submerged 
valleys are thought to have been formed by rivers when the areas 
where they occur were land. 

(4) Examples of mountain-like swells are furnished by Cuba and 
the adjacent islands, which are really the crests, of a great mountain 
system rising from deep water. 

(5) An example of the plateau type of elevation is the Dolphin 
Ridge of the Atlantic (Fig. 122). This broad, low, north-south swell 
extends to latitude 40 S., and divides the basin of the Atlantic into 
two troughs, where the water is deeper than over the ridge. In the 
southern Pacific, many volcanic islands rise from similar submarine 
plateaus. 

Composition of sea-water. One hundred pounds of average 
sea- water contain nearly three and one-half (3.44) pounds of dissolved 
mineral matter. More than three-fourths (nearly 78 per cent) of 
this is common salt, but nearly all other substances found in the 
earth's crust are present, most of them in very small quantities. 
. Even gold occurs in sea- water, but not in quantity sufficient to make 
its extraction profitable. If all the salts dissolved in the sea were 
taken out of solution and laid down as solid matter on the ocean-bot- 
tom, they would make a layer about 175 feet thick. In the past, the 
evaporation of water from salt lakes, perhaps cut off from the sea by 
changes of level, has formed important salt-beds. New York has a 



236 ELEMENTS OF GEOGRAPHY 

valuable salt industry near Syracuse, depending on such deposits of 
rock salt (p. 288), while the great salt mines near Salzburg and Cracow, 
in Austria-Hungary, are famous the world over. Much salt is 
obtained also by evaporating sea-water. The Stassfurth salts, con- 
taining much potash, are important factors in making Germany the 
leading nation of the world in chemical industries. 

The mineral matter in sea-water makes it a little heavier than 
fresh water, and makes it freeze less readily. Its lower freezing point 
(26°-28° F.) often leaves the ocean free from ice when near-by bodies 
of fresh water are frozen over. 

Sources of mineral matter. Dissolved mineral matter is being 
carried to the sea by rivers all the time. Rivers have brought the 
sea most of its mineral matter, though some of it may have been dis- 
solved from rocks beneath the sea, or about its shores. The mineral 
matter carried in solution to the sea by rivers in a year would make 
nearly half a cubic mile of solid matter. 

The minerals which are most plentiful in the sea are not those 
which are most common in the rocks of the land. Those minerals of 
the land which are dissolved most easily get into rivers, and thence 
to the sea, in greater quantity than those which are less soluble. 
Some of the minerals in sea-water, such as salt, do not exist in the 
common rocks of the land. Common salt is made by the union of a 
substance in certain rocks with a gas in the air or water. Granite, 
for example, contains sodium, one of the elements of salt, and when 
sodium unites with chlorine (a gas) the result is salt. It takes much 
granite to yield the sodium for a little salt. 

Withdrawal of mineral matter from the sea. Of the mineral 
matter carried in solution to the sea, calcium carbonate, of which 
most shells are made, is most important to ocean life. The amount of 
this substance dissolved in river-water is nearly as great as that of 
all others. Common salt is present in river-water in amounts too 
small to be tasted; yet the amount of it in sea- water is more than 200 
times that of calcium carbonate. The reason is that calcium carbon- 
ate is taken out of the water all the time by animals, to make shells, 
coral, etc., while most of the salt carried to the sea stays in the water;, 
and this probably has been true for millions of years. 

Gases in sea-water. Sea-water also contains dissolved gases. 
The most abundant are those of the air, especially nitrogen, oxygen, 
and carbon dioxide. The amount of oxygen dissolved in the ocean 



THE OCEANS 237 

is more than 3-^ of that in the air; the amount of nitrogen about yio" 
that of the air, while the amount of carbon dioxide in the sea is iS 
times that in the air. 

Much of the gas in the ocean was dissolved from the atmosphere. 
After being taken into solution at the surface, the gases are distributed 
through the whole ocean, partly by movements of the water, and 
partly in other ways. Thus oxygen has been found in samples of 
water from great depths. 

The oxygen of the water is being used all the time by sea animals, 
and its supply is being renewed all the time by solution from the air. 
Animals and plants do not use the nitrogen dissolved in sea-water, 
and the same nitrogen probably stays there from age to age. The 
carbon dioxide is being used all the time by the plants of the sea, and 
some of it is constantly escaping into the air. 

Salinity, density, and movement. For several reasons, some 
parts of the sea are more salty than others. (1) The salt is left behind 
when ocean-water evaporates. Since evaporation is more rapid in 
some places than in others, the water becomes more salty where 
evaporation is great, as in some hot climates. (2) Where much rain 
falls, the water is freshened. (3) Where large rivers enter the sea, the 
latter is freshened. In these ways the saltness of the sea-water at 
the top of the ocean is changed all the time. 

Every change in the saltness of sea-water changes its density, and 
unequal density causes movement. When surface water becomes 
denser than that beneath, it sinks, and lighter water comes in over 
it from all sides. When the surface water of one place becomes less 
dense (fresher) than that about it, the lighter water spreads out on 
the surface, as oil spreads on water. Since variations in saltness are 
being produced all the time, motion due to unequal density is constant. 
Movements brought about in this way are usually very slow, and are 
called creep. 

Salinity and color. The sea is generally blue or green, but 
its color varies from place to place and from time to time. The 
blue is deeper where the amount of salt is great. Thus seas like the 
Mediterranean, which are more saline than the open ocean (Why?), 
are of deeper blue. The cold and less salty (Why?) waters of high 
latitudes are often distinctly green. Many variations of color are 
due to tiny particles of solid matter suspended in the water. Micro- 
scopic animals and plants (as in the Red Sea), sediment from the 



2 3 8 



ELEMENTS OF GEOGRAPHY 



land (as about the mouth of the Hwang-ho), and material from vol- 
canoes beneath the sea, all help to give the sea-water of different 
places its various colors. 

Temperature of the Sea 

Temperature of the surface. The surface of the ocean, like 
that of the land, is warmer near the equator and cooler toward the 
poles (Fig. 123). Near the equator its temperature is about 8o° F.; 




Fig. 123. Map showing mean annual temperatures for the surface waters of 
the oceans. (After Lyde.) 

near the poles, where not frozen, it is 26°-28° F. When the tempera- 
ture becomes colder, sea-water freezes, and the surface of the ice 
may become as cold as the air above it; but the temperature of the 
water just beneath the ice is 26°-28° F. The decrease of temperature 
toward the poles is by no means regular, as shown by the isothermal 
chart (Fig. 123), where isothermal lines over the ocean are not 
parallel with the parallels of latitude. 

In the open sea, ocean currents help to make the isotherms depart 
from the parallels (p. 77). Some currents are cold, flowing into 
warmer water, and some are warm, flowing into cooler water. 

There are still other reasons why the surface of the ocean does not 



A 



THE OCEANS 



239 



get colder steadily from equator to poles. Rivers help to make sur- 
face temperatures unequal, for they are often warmer than the sea 
in summer, and colder in winter. Partly enclosed arms of the sea in 
low latitudes are warmer than the open ocean in the same latitude 
(Fig. 124; Why?). The highest temperatures of the sea are found 
in such situations. The surface temperature of the Red Sea, for 
example, sometimes reaches ioo° F. 

Temperature and movement. Water expands slightly when 
warmed. Warm water is therefore lighter than cold water, if both 
are equally salt. It follows that unequal surface temperatures cause 
movement of the surface waters, and since the surface temperature 



Indian Ocean 



Red Sea 




Fig. 124. Diagrammatic section of Red Sea and adjacent part of Indian 
Ocean, to illustrate the effect of a barrier on the temperature of the water. Tem- 
peratures are in degrees Fahr. 

is kept unequal all the time by unequal heating, by inflow of rivers, 
and by melting ice, there is constant though slow movement of the 
surface waters. 

Temperature beneath the surface. Sea-water becomes cooler 
with increasing depth, except where the surface is at or near the 
freezing point. ' Even where the surface water is warmest} the 
temperature at a depth of a few hundred fathoms is below 40 F. 
The following table shows the average temperature of the sea at 
various depths, in lower latitudes: 

Average 
Depth Temperature 

600 feet 60 . 7 

1,200 feet 50. o° 

3,000 feet 40 . i° 

6,000 feet 36 . 5 

13,200 feet 35-2° 



It is estimated that not more than one-fifth of the water of the 
ocean has a temperature as high as 40 F., while its average tempera- 
ture is probably below 39° F. At the bottom of the deep sea the 



240 ELEMENTS OF GEOGRAPHY 

temperature of the water is generally below 35 F.; only in certain 
areas of shallow water, and in the partly enclosed seas of relatively 
low latitudes, is the temperature of the bottom as high as 40 . Thus 
the deeper parts of the Caribbean Sea (over 2,000 fathoms) have a 
temperature of 39° to 40 . This is the temperature found in the 
open Atlantic at a depth of about 900 fathoms, the level of the bot- 
tom of the deepest channel connecting the Caribbean and the ocean. 
The Mediterranean also has practically the same temperature at all 
depths below the level of its deepest connection with the Atlantic. 



Movements of Sea-Water 
Causes 

We have seen that differences in saltness and in temperature 
make waters unequal in density, and so produce a slow circulation of 
the waters of the sea. There are other causes which produce move- 
ment, such as (1) differences of level, (2) winds, (3) the attraction of 
the moon and the sun, and (4) occasional causes, such as earthquakes 
and volcanic explosions. 

Inequalities of level. The inequalities of level which produce 
movements of sea- water are brought about chiefly by (1) the 
discharge of rivers, which raises the surface of the sea near their 
mouths; (2) winds, which pile up the waters along the shores against 
which they blow; (3) unequal rainfall, which raises the surface most 
where most rain falls; and (4) unequal evaporation, which lowers the 
surface most where it is greatest. 

Movements due to unequal rainfall and evaporation are generally 
too slight to be observed. Those caused by the inflow of rivers and 
by winds are greater. Thus, beyond the mouth of a great river like 
the Amazon, movement may be distinct for many miles, and waters 
often are piled up against a shore by winds, to such an extent that the 
rise may be seen readily. The raising of the surface of the water 
caused most of the destruction in the storm at Galveston (p. 139). 
Strong southeasterly winds frequently pile up the water sufficiently to 
block the sewers in Baltimore, while embankments have been con- 
structed to protect the eastern part of New Orleans from the waters 
of Lake Pontchar train. When the water-level has been raised along 
a coast by the wind, it settles back after the wind goes down. 
Since the causes producing differences of level are always in operation, 
movements due to these differences are always taking place. 



THE OCEANS 241 

Winds. Winds produce movement of sea-water in another way. 
Where they have a constant direction, as in the zone of trades 
(p. 166), there is a constant drifting movement of surface water in 
one direction. A steady movement in one direction necessitates a 
return movement somewhere else, thus producing a circulation of the 
sea-water. Where the circulation is in the form of distinct streams 
of water, they are called ocean currents. 

Attractions of moon and sun. Bodies attract each other in 
proportion to their masses, and inversely as the squares of their 
distances. That is, a body which weighs twice as much as another 
has twice the attractive force at the same distance. If one of two 
bodies of the same mass (or weight) is twice as far from a third body 
as the other is, their attractive forces on the third are as 1 14. 

The side of the earth toward the moon is nearer the moon (by 
about 4,000 miles) than the center of the earth is, and so is attracted 
by that body more strongly than the center. The opposite side (about 
4,000 miles farther away) is attracted less strongly than the center, 
and these differences of attraction disturb the waters of the earth. 
The attraction of the sun produces similar, though lesser, effects. 
The resulting movements of the sea- water are tides (p. 246). 

Occasional causes. Landslides along shore, earthquakes, vol- 
canic explosions, etc., may cause sudden and extensive movements 
of the ocean-water (pp. 298, 306). Low coastal lands occasionally 
suffer severely from movements of this sort. 

Types of Movement 

The movements which result from the above causes are (1) 
waves, with the undertow and shore currents which they produce; 
(2) ocean currents; (3) drift, or feeble currents; (4) tides; and (5) creep 
(p. 237). 

Waves. When the wind blows over a water surface it causes 
waves. The stronger the winds, the greater the waves. With 
moderate winds, waves in open water rarely exceed 10 feet in height 
(from crest to trough). Ordinary storm- waves may be twice as high, 
while in violent storms a height of 40 or more feet is attained. Such 
waves breaking on the decks of vessels may do much damage. Many 
vessels have obtained relief from storm- waves by allowing oil to drip 
from a bag hanging at the bow or stern. The oil spreads over the 
surface in a thin film, and since the friction of the wind on the oil- 
covered surface is much less than on a surface of water, the waves 



242 ELEMENTS OF GEOGRAPHY 

decrease in size. Storm-waves attain a rate of 30 miles an hour very 
commonly, and reach the speed of 60 miles an hour in violent hurri- 
canes, but, save in shallow water, the water in a wave usually does not 
move forward (p. 520). 

The distance between successive wave crests is the length of the 
wave, and the time between the passage of successive crests is the 
period of the wave. Both length and period vary widely, and are 
important in navigation. Wave lengths vary from 100 feet or less 
to 2,000 feet or more, in severe storms. Occasionally the surface of 
the ocean is smooth and glassy, and yet shows long, low undulations. 
These are " swells," and usually represent waves caused by distant 
storms. On some coasts they interfere seriously with commerce. 
The shortest waves are usually found where there is an actual move- 
ment (current) of the water contrary to the direction of the wave im- 
pulse, giving a " choppy sea." Such waves are especially unfavorable 
for small craft, and may cause much discomfort to passengers on 
larger vessels. In general, the longer the vessel, the less it is affected 
by waves; hence the advantage of the modern ocean steamships,, 
which in some cases are nearly twice as long as the average storm- 
wave (400 to 600 feet). 

Currents and drifts. There are more or less distinct streams 
of water, or currents, in various parts of the ocean. This was known 
first by their effect on the course of sailing vessels. It was later proved 
in other ways, as by following the course of floating objects set adrift 
for this purpose. 

It is desirable to know as much as possible about these currents 
because of their effect on navigation. In foggy weather, and espe- 
cially near some coasts, failure to allow for the current may lead to 
ship-wreck. Some of the wrecks that have occurred on the Irish coast 
probably were caused in this way. Vessels are aided or retarded by 
currents, according to the direction of the voyage. 

Surface currents also affect the movements of icebergs and floe 
ice. Collision with an iceberg might wreck the largest steamship, 
and floating ice favors the formation of fog, which increases the 
danger of collision between vessels, and between vessels and ice. 
For these reasons, steamship routes across the North Atlantic vary 
somewhat with the season, in order to avoid the floating ice. 

Little is known of ocean currents beneath the surface. A few of 
them affect the water to a depth of 3,000 feet, but most of them are 
shallow, compared with the depth of the ocean. Even the larger 



A 



THE OCEANS 243 

currents are not always seen easily, though they differ from the 
water on either side in color, temperature, and salinity. As a rule, 
these differences are more marked the swifter the current. A current 
so slow as to be indistinct is often called drift. 

Courses and causes of ocean currents. Fig. 125 shows the 
general circulation of the surface waters of the sea. It represents a 
large part of the surface water as moving. There are equatorial 
currents or drifts moving westward, one on each side of the equator, 
in both the Atlantic and Pacific oceans. Between the equatorial 
currents, there is, in each of these oceans, a narrow counter-current, 
or drift, moving eastward. The equatorial waters of the Atlantic 
Ocean which are drifting westward are divided at the eastern coast 
of South America. The smaller part is turned to the southwest, and 
the larger part to the northwest, along the border of the continent. 
Part of the northern branch flows through the Caribbean Sea into 
the Gulf of Mexico, whence it issues through the narrow strait between 
Cuba and Florida as the Gulf Stream. This well-defined current is 
fed partly by the water which enters the Gulf from the equatorial 
drift, and partly by that which enters from the land. 

In the Straits of Florida, the Gulf Stream is about 40 miles wide 
in its narrowest part, 2,000 to 3,000 feet deep, and has a maximum 
velocity of about five miles per hour. Farther north, it becomes 
wider and slower, until, in the open ocean, the rate is perhaps only 
10 to 15 miles per day. As it becomes slow, its boundaries become 
less distinct, and it is recognized by its temperature, color, and life 
more readily than by its motion. 

As it advances, the Gulf Stream turns toward the east (to the 
right), crosses the Atlantic, and approaches the coast of Europe in a 
latitude farther north than that where it leaves the coast of America. 
As it approaches Europe, it divides and spreads, but long before 
Europe is reached (about latitude 40 N.), the current has become 
a wide-spread drift of water, not easily distinguished. This favorable 
current and westerly winds make the voyage for sailing vessels 
from this country to England much quicker than the return trip. 
That part of the equatorial drift which is turned southward along the 
coast of South America soon turns to the left (Fig. 125). 

The equatorial drifts of the Pacific follow courses similar to those 
of the Atlantic. The part which turns north is the Japan Current. 
The Indian Ocean has a south equatorial drift only, and its course 
corresponds to that of the southern part of the equatorial drifts of 



244 



ELEMENTS OF GEOGRAPHY 




THE OCEANS 245 

the other oceans. All currents moving toward the poles from the 
equatorial region are warm currents. 

The poleward movement of warm waters makes a return equa- 
torward movement necessary. The cold waters moving toward the 
equator are turned to the right in the northern hemisphere, and to 
the left in the southern. The result is to throw them to the eastern 
coasts of the continents, where in places they form distinct cold 
currents. Along the east coast of North America, the Labrador Cur- 
rent brings icebergs south to Newfoundland, while in the warmer 
waters of the northeastern Atlantic, ice rarely forms even in lati- 
tude 70 . The Labrador Current chills the air above it, and this 
makes northeast winds in New England colder than they would 
be otherwise. 

The equatorial drifts are caused and directed by the trade-winds. 
Outside the tropics the winds do not blow in one direction all the 
time, and so do not produce persistent drifts or currents; but in 
regions of strong monsoon winds, as about India, the drift of the sur- 
face waters changes with the wind (Figs. 64 and 66). 

If the ocean covered all the earth, the westward drift of equatorial 
waters, caused by the trade-winds, would go round and round the 
earth. But the continents deflect the waters, turning them north 
and south. Once turned in these directions, the waters would tend 
to follow the coasts but for the deflecting influence of the earth's 
rotation. Where the sea is so shallow that the moving water touches 
bottom, the topography of the bottom influences the course of move- 
ment. Ocean currents therefore appear to be started chiefly by the 
winds, and to be directed by winds, lands, and the rotation of the 
earth, and, to a less extent, by the topography of the bottom. 

Ocean currents and atmospheric temperatures. Without 
ocean currents, the isotherms over the sea would follow the parallels 
somewhat closely, except near the continents (p. 75). Under such 
conditions, the temperature over the ocean in the latitude of the 
British Isles and northward would be io° F. or more lower than now 
(Fig. 123). Ocean currents do not themselves warm or cool the land; 
but the air over a warm current is warmed by the water, and is then 
blown to the land. Even without the Gulf Stream, the western coast 
of Europe would have a milder winter climate than the eastern coast 
of North America in corresponding latitudes (p. 191), but the drift 
of warm water into the North Atlantic makes the winter temperature 
of Europe north of latitude 50 considerably warmer than it would 
be otherwise. Thus the harbor of Hammerfest, Norway, latitude 



246 ELEMENTS OF GEOGRAPHY 

7 6°, is affected by ice about as much as that of New York, latitude 
40 . The Japan Current likewise lessens the cold of winter on the 
northwestern coast of North America. Similar results would be 
found in the southern hemisphere, if there were land so situated as to 
feel the effects of the warm currents in the southern oceans. 

Warm currents often help to cause fogs, both at sea and on 
land. When wind blows over a warm current, it takes up a large sup- 
ply of moisture. If it then blows over colder water, it is cooled, and 
some of its moisture is condensed, producing a fog. Fogs are common 
along the leeward side of the Gulf Stream, where the adjacent land or 
water is much cooler than the current itself. Fogs are more abun- 
dant about Newfoundland than farther south, because the difference 
between the temperature of the Gulf Stream and its surroundings is 
greater there than farther south. 

The shifting of the course of the Gulf Stream sometimes is men- 
tioned in newspapers as the cause of a mild winter in the United 
States. Strong winds may force the surface waters of the Gulf 
Stream out of their usual course; but this shifting is always tempor- 
ary, and has little or no effect on the winters. 

Work of ocean currents. Currents have little effect on the 
ocean-bottom, and almost none on coasts, because in most places they 
touch neither; but where the water is shallow, a current may scour the 
bottom, as the Gulf Stream does between Florida and Cuba. Since 
ocean currents erode but little, they carry little sediment. Warm 
currents carry multitudes of plants and animals, many of which are 
very small, and these organisms and their shells are scattered far and 
wide over the bottom of the ocean. Currents may also carry wreckage 
of ships and driftwood long distances. In some places the latter is a 
valuable source of fuel. Seeds may be carried long distances in the 
same way. 

Tides. Along most coasts, the ocean-water rises and falls twice 
every day, or, more exactly, every 24 hours and 52 minutes. The rise 
and fall of the water are the tides. The tide rises for about six hours, 
when it is high or flood tide, and then falls for about six hours, when it is 
low or ebb tide. In most places there is a distinct interval of little or no 
movement ("slack water") when high tide changes toward low, and 
vice versa. The rise and fall amount to several (3 to 6) feet in most 
places. In bays which open broadly to the. sea, but are narrow 
at their heads, the range is sometimes 20 or 30 feet, and in rare cases, as 
in the Bay of Fundy (Figs. 126 and 127), 50 feet or more. Conversely, 



I 






THE OCEANS 



247 



where bays have a narrow entrance and widen within, the tidal range 
is small. Tides are absent in small lakes, and are feeble in large 
lakes and in seas connected with the ocean by a narrow passage, such 




Fig. 126. Low tide at Wolfeville, Bay of Fundy, Nova Scotia, Sept., 1903. 
In March, 1904, end of pier was washed away in a storm, and lighthouse damaged. 
(Photograph by the late Roland Hayward, Milton, Mass.) 

as the Mediterranean Sea and the Gulf of. Mexico. Thus at Gal- 
veston, Texas, the range of the tide is less than one foot. 

In many shallow harbors, the tides have an important effect on 
navigation (Figs. 126 and 127). Even some of the most important 




Fig. 127. High tide at the same place shown in Fig. 126. (Photograph by 
the late Roland Hayward, Milton, Mass.) 

ports depend on the rise of the tide for the movement of their com- 
merce. Thus at Liverpool vessels arriving at low tide must wait, in 
many cases, for high tide, before the water is deep enough for them to 



248 



ELEMENTS OF GEOGRAPHY 



dock, and vessels must arrange hours of departure to match high tides. 
Hence, it is important for the navigator to know exactly the hours 
of high and low tide for every harbor which he may wish to enter. 
Where the tide runs in among islands, or passes through narrow 
straits, it causes distinct currents {tidal races), eddies, and whirlpools, 
like the famous Maelstrom near the Lofoten Islands. These move- 
ments may interfere with navigation, especially by small boats. 
Sailing vessels frequently have serious difficulties with tidal races, as 
at Hell Gate, New York, and in Vineyard and Nantucket sounds, off 
the coast of Massachusetts. Fishermen commonly speak of the tide 




Fig. 128. Tidal bore entering river at Moncton, New Brunswick, 
graph by the late Roland Hayward, Milton, Mass.) 



(Photo- 



as "coming in," or "going out," and time their movements to take 
advantage of it. Small craft find it impossible to go out when the 
tide is coming in, or to come in when the tide is going out. Even 
large vessels are affected by the "set" of the tides, and more than one 
wreck has been due to this cause. In many ways these movements of 
the ocean are more important to navigation than ocean currents, and 
much effort is devoted to charting them for the benefit of navigators. 

The tide runs far up many rivers. Thus the range at Troy, some 
150 miles up the Hudson River, is more than two feet, and tides 
ascend the St. Lawrence nearly 300 miles. As the tide advances up 
the channel, its front may become a steep, wall-like wave called a 
bore (Fig. 128). This is the case in the Severn, Seine, Tsien-Tang- 
Kiang, and other rivers. In the last-named river the waves are 
sometimes 25 feet high, and advance at the rate of 10 to 20 miles an 
hour. Such conditions are dangerous for shipping, and serious losses 
of life and property frequently result. 

It is at least two thousand years since the moon was first 



THE OCEANS 249 

thought to cause the tides, but only about two hundred years since 
Newton explained how the moon produces them. The moon rises 
and sets twenty-four hours and fifty-two minutes later each day 
than it did the day before. The time between two high tides or 
between two low tides is half this period. It appears to have been 
this fact which suggested that the tides are caused by the moon. 

Without attempting to give a full explanation of the tides, some 
of the principles involved may be understood. If a weight is 
attached to a string and whirled, it tends to fly away in a 
straight line. It is prevented from doing so by the string, which 
holds it in its circular path. The tendency to fly away is what 








Fig. 129. Diagram to show the tendency of the moon to raise the water on 
the side of the earth toward the moon and on the opposite side at the same time, 
producing two hieh tides. 

is called centrifugal force. The earth and moon attract each other 
(p. 241), and would fall together but for the centrifugal force due to 
their motions. At the center of the earth, and at the center of the 
moon, the attraction between these bodies is exactly balanced by the 
centrifugal force due to their revolutions. The result is that neither 
falls toward the other. But on the side of the earth nearest the moon 
the attraction is stronger than at the center of the earth (p. 241), and 
is greater than the centrifugal tendency. The attraction of the moon, 
therefore, tends to make the earth bulge out on the side nearest the moon. 
On the opposite side of the earth the attraction is-weaker than at the 
center, and is less than the centrifugal force. Here, too, the earth 
tends to bulge out. The solid part of the earth is so rigid that it does 
not rise enough to be felt or seen. But the waters of the ocean move 
easily, and rise a little, and the rise takes place on opposite sides of the 
earth at the same time. This makes the high tides. Between the 
high tides the water sinks a little, making the low tides. The rotation 
of the earth makes the tides appear to move about the earth. 

If all the earth were covered with water, its surface would have 
two great tidal bulges or waves at the same time (Fig. 129). The 



25o ELEMENTS OF GEOGRAPHY 






highest part of one would be a point directly under the moon, and the 
highest point of the other would be opposite the first. Each wave 
would cover half the earth, and the borders of the two would meet in 
a great circle,, where the surface of the water would be lowest. 

If the moon were not revolving about the earth, high tide at any 
place would come every 12 hours. But the moon moves forward in 
its orbit about the earth, so that it takes 24 hours and 52 minutes for 
a given place to have the same relation to the moon that it had the 
day before. This makes the period between successive high tides 
12 hours and 26 minutes. 

The movements of the tides are not so simple as the outline above 
would imply. Many things interfere. The continents stop or divert 





Fig. 130. Diagram to show the relative positions of the earth, moon, and sun, 
at the time of new moon ( = spring tide). Size of moon (M)' and earth (E) great- 
ly exaggerated. 

the advance of tidal waves, and the waves travel more slowly in shallow 
than in deep water (Why?). Since tides are retarded most near land, 
their advance is here most irregular. For these reasons, the time of 
high tide at most places differs from the time when the moon crosses 
their respective meridians. This difference in the time of arrival of 
high or low tide may be determined for any harbor, and is called the 
"establishment of the port." At New York, for example, high 
water arrives 8 hours and 13 minutes after the moon passes the 
meridian. Tables showing the "establishment" of different ports 
are of great value to navigators. 

The sun also attracts the earth, and tends to cause tides. If 
there were no moon we should still have small tides produced by the 
sun. The tides which we know are the combined effects of moon and 
sun; but the moon's tides are much the stronger. The sun strength- 
ens the tides when sun and moon work together, and weakens them 
when they work against each other. 

When sun and moon stand in the relation to each other and to 
the earth shown in Fig. 130 (new moon), each tends to make high 
tides at A and at B. When the relations are those shown in Fig. 131 



THE OCEANS 251 

(full moon), the result is the same. At these times, and each occurs 
once a month, high tides are higher, and low tides lower, than at 
other times. The tides of such times are called spring tides. They 
have no relation to the spring season. 

When the earth, moon, and sun have the relative positions shown 
in Fig. 132, and this occurs twice each month, the tidal influences of 





Fig. 131. Diagram to show the relative positions of the earth, moon and sun, 
at the time of full moon ( = spring tide). 

the sun and the moon are opposed to each other, and the result is 
that high tides are not so high, nor low tides so low, as under other 
conditions. The tides of such times are known as neap tides. Spring 
tides have nearly twice the range of neap tides in many places. 

In the open ocean and along precipitous coasts, the tide is like 
other waves, merely a rising and falling of the water. Like other 





Fig. 132. Diagram showing the tendency of the sun and moon to produce 
tides on opposite parts of the earth at the time half way between new moon and 
full moon, and half way between full moon and new moon. 

waves also, the water of the tidal wave moves forward when it 
approaches shores where the water is shallow. 

In shallow waters near the coast, tides alternately cover and 
expose wide expanses of sandy .beach or mud flats, as the case may 
be. The water-line at low tide may be a quarter of a mile or more 
from its position at high tide. Tidal currents may be effective agents 
of erosion. Tidal scour keeps many waterways (thorofares) open 



252 ELEMENTS OF GEOGRAPHY 

through tidal marshes, as along the coast of New Jersey. It also 
maintains deep channels in certain harbors, to the great advantage 
of commerce. By the circulation they cause, tides in some cases 
help to remove filth which otherwise would accumulate in harbors. 
Sewage disposal is always easier for cities near tide-water. On the 
other hand, the gradational effect of tides is harmful in some cases, 
for much of the sediment drifted about by them is deposited in har- 
bors. This makes expensive dredging necessary in many harbors, in 
order to maintain a sufficient depth of water for shipping. The 
frequent shifting of the deposits renders it impossible to indicate the 
channel on the pilot charts of some harbors. 

The large volume of water rising and falling in tides has led to 
many attempts to develop tidal water power. Small tide mills are 
used for grinding grain and other purposes at various places in western 
Europe, and a few larger power plants have proved useful, as in the 
Seine estuary. But on most coasts conditions are not favorable for 
the development of extensive power from tides. The chief difficulties 
are the slight rise and fall, and the slow rate of movement. 



The Life of the Sea 

Animals and plants abound at and near the surface of the sea, 
and at the bottom where the water is shallow. A bucket of water 
dipped up from the surface of the ocean almost anywhere will con- 
tain hundreds or even thousands of minute plants and animals, though 
most of them are too small to be seen without a microscope. Liv- 
ing things are present, but not in great numbers, at the bottom of 
the deep sea; but in the water between the uppermost ioo fathoms 
and the bottom, animals and plants are nearly absent. It has been 
estimated that the life of the sea exceeds that of the land, square 
mile for square mile, but there is probably no one level in the sea 
where life is so abundant as on the fertile parts of the land. 

The temperature, the depth, the clearness, the saltness, and the 
quietness or roughness of the water, influence the life which it con- 
tains, in ways easily understood. The depth of the water affects the 
distribution of the plants and animals which live on the bottom, but 
has little effect on those which floater swim near the surface. The 
most important influence of depth appears to be in connection with 
light and oxygen. Animals cannot see much at a depth of more 
than about 50 fathoms, though a little light penetrates to greater 



THE OCEANS 253 

depths. In the great body of the ocean darkness reigns, and green 
plants, which depend directly on sunlight, cannot live in darkness. 
At the bottom of the deep sea the water is not stirred, and any oxygen 
it contains must pass down from the surface after being dissolved 
there. As it is used up by the animals at the bottom, the supply is 
renewed from above very slowly. 

Though the pressure of the water at the bottom of the ocean is 
very great (p. 233), the animals living there can stand it, because their 
bodies are full of liquids under the same pressure, and these great 
pressures within their bodies balance the great pressures without. 
If an animal from the bottom of the deep sea were brought suddenly 
to the surface it would explode (Why?). Even when raised slowly, 
they sometimes explode as they near the surface. 

Some animals, such as the polyps which make coral, live only in 
warm regions where the water is shallow and clear, with neither 
excess nor shortage of salt. Others, such as narwhals and seals, are 
found only in cold waters. Still others are found in both warm and 
cold waters. The unequal distribution of ocean temperatures by 
warm and cold currents influences" greatly the character of marine 
life in different parts of the sea. Thus coral polyps cannot live about 
the Galapagos Islands (Why?), near the equator, while they are 
abundant about the Bermuda Islands, in latitude 32 N. Oysters 
thrive on the south side of Cape Cod, but are practically absent from 
the colder waters north of the Cape. 

In many ways the life of the sea is in strong contrast with that of 
the land. Thus most familiar land plants are fixed in position, but 
many sea plants float. Most land animals are free to move about, 
while many of those in the sea, such as polyps and barnacles, are 
fixed through most of their lives. Many which are not fixed move 
about but little, either lying on the bottom or burrowing into it. 
Some, on the other hand, as many of those in the surface waters 
(pelagic life), appear to be moving always. 

All the great groups of animal life are represented in the sea. 
Even warm-blooded mammals (whales, seals, walruses, etc.) abound 
in frigid waters, among icebergs and ice-floes. Some of them, like 
the seals and walruses, do not spend all their time in the water, but 
frequently crawl up on the ice or land. The varieties of plant life are 
many, but the forms we are most familiar with on land are wanting. 

Not only are there many varieties of marine plants and animals, 
but the largest modern animals (whales) live in the sea. Many sea 



254 ELEMENTS OF GEOGRAPHY 

plants, too, are of great size. Some sea-weeds are six inches in diam- 
eter, and some have a length greater than that of the tallest trees. 
They are, however, not so bulky as large trees, and the amount of 
solid matter which the largest sea- weed contains is far less than that 
of the largest tree. This would be seen if the large sea-weeds were 
allowed to dry. 

The life of the sea is important in many ways. Fish, oysters, clams, 
crabs, lobsters, etc., are used for food (p. 561). The total value of 
food products derived from the sea probably is not less than $500,000,- 
000 per year. The best fishing regions are found where large areas of 
shallow water (as over broad continental shelves) furnish extensive 
feeding and breeding grounds for vast numbers of fish. The most 
important region of this sort is the shallow water about the British 
Isles, including the North Sea. The British fisheries alone employ 
more than 100,000 men, and yield an annual catch valued at more 
than $50,000,000. Similar conditions led to the development of 
important fisheries from New England, especially from Massachusetts 
and Maine (p. 562). 

Other animals furnish other articles of commerce. For example, 
the seal furnishes fur and oil; the whale, oil and whalebone; and the 
hide of the walrus makes exceptionally strong leather. Coral and 
sponges, products of animal life, are also articles of commerce. The 
supply of lime for fertilizer, as well as for plaster, mortar, cement, and 
concrete, comes chiefly from limestone, most of which is composed of 
the secretions of sea animals. Sea-weed was used formerly as the 
chief source of soda and of iodine. Some varieties still are gathered 
in large quantities on the coast of Massachusetts and Europe, to be 
used as food under the name of "Irish moss." 

Coral reefs. The little polyps (Fig. 133) which secrete coral 
live where the water (1) is 120 feet or less in depth, (2) is never colder 
than about 68° F., (3) has the saltness of normal sea- water, (4) is 
nearly free from sediment, and (5) is subject to some movement by 
the wind. Where these conditions exist, polyps thrive and. make 
reefs, and the reefs may become islands. Polyps flourish along the 
borders of many tropical lands, and in some places far from shore. 

Coral reefs are of several classes. Those which are separated from 
the land by a somewhat deep channel or lagoon are barrier reefs. 
Those close to the land are fringing reefs. Rudely circular reefs 
inclosing a central lagoon are atolls. The chief importance of coral 
reefs is their relation to navigation. Atolls frequently afford shelter 



THE OCEANS 



255 



to vessels in distress, far from the mainland. Submerged reefs, how- 
ever, are dangerous, and long barrier reefs may hamper commerce 
seriously. Thus the Great Barrier Reef extends along the east coast 
of Australia for 1,000 miles. It is broken by many inlets, but only 
a few of them allow the passage of vessels. Within the reef the water 
is calm and favorable for steamships, but dangerous for sailing 




Fig. 133. Coral formations, Samoa. (Muir and Moodie.) 

vessels, which are affected more by the winds. Partly because of the 
reef, no important port is found along this part of the coast. 

The use of pink or red coral for jewelry leads to important coral 
"fishing" in the Mediterranean, whence much of the product goes to 
India. 

Most of the natives of coral islands are backward in civilization, 
because of the limitation of their resources. 



Questions 

1. Why is agriculture possible on a limited scale in Alaska, and not in the 
same latitudes in Labrador, Greenland, and Baffin Land? 

2. Why is Alaska less favorable for agriculture than Norway? 

3. Why is the climate in latitude 50 , on the west coast of South America, 
less favorable for farming than that in latitude 50 on the west coast of North 
America? 



256 ELEMENTS OF GEOGRAPHY 

4. Why are isotherms affected less by ocean currents in the southern hemi- 
sphere than in the northern? 

5. On which side of the Gulf Stream, in latitude 45°, are fogs more 
common? Why? 

6. Are fogs more likely to occur over a warm current, or over a cold one? 
Why? 

7. In order to enter a shallow harbor, is a vessel more likely to have to wait 
for flood tide, at the time of neap tides or at the time of spring tides? Why? 

8. What inference might be drawn from the fact that polyps once lived within 
the Arctic Circle? 

9. What changes in geography are implied by the fact that polyps once lived 
in eastern Wisconsin? 

10. How would the general conditions of climate and commerce be changed 
if the oceans were where the continents are, and the continents were where the 
oceans are? 

11. Why are steamer routes across the Atlantic farther south in summer 
than in winter? 

12. Why do several steamship routes (Fig. 113) converge at the mouths of 
many large rivers? 

13. Why are there so few steamship lines (Fig. 113) crossing the South Pacific 
and South Atlantic oceans? 

14. Why is the water along the equator in the Pacific Ocean warmer toward 
the western border of the ocean? What does the principle involved suggest in 
regard to the surface temperatures in the Gulf of Mexico? 



References 

Austin : Problems of the Pacific — Commerce of the Great Ocean, in Nat. Geog. 
Mag., Vol. XIII, pp. 303-318. 

Church: Interoceanic Communication on the Western Continent, in Geog. 
Jour., Vol. XXI, pp. 3I3-353- 

Cornish: Dimensions of Deep Sea Waves, in Geog. Jour., Vol. XXIII, pp. 
423-444. 

Johnson, E. R.: Elements of Transportation, Ch. XXVII. (New York, 
1909.) 

Johnstone: Conditions of Life in the Sea. (Cambridge, Eng., 1908.) 

Kirchoff: Man and Earth, Ch. II. (London.) 

Maury: Physical Geography of the Sea. (New York, 1856.) 

Murray: Articles on oceanography in Geog. Jour., Vol. XII, pp. 1 13-137; 
Vol. XIV, pp. 34-50, 426-441; Scot. Geog. Mag., Vol. XV, pp. 505-522. 

Semple: A Comparative Study of the Atlantic and Pacific Oceans, in Jour. 
Sch. Geog., Vol. Ill, pp. 121-129, 172-179. 

Shaler: Sea and Land. (New York, 1894.) 

Smith, J. R.: The Ocean Carrier, Chs. I, II, III. (New York, 1908.) 

Thomson: The Depths of the Sea. (London, 1874.) 

Wild: Thalassa. (London, 1877.) 



CHAPTER XIII 
THE MATERIALS OF THE LAND AND THEIR USES 

General Constitution 

The mantle rock. Loose material such as clay, sand, and gravel, 
covers most of the land. This cover ranges in thickness from a few 
inches to scores or even hundreds of feet, and is called mantle rock, 
because it forms a mantle over the underlying rock, which in most 
places is solid. Mantle rock, which is formed by the decay and break- 
ing up of solid rock, is called also rock waste. 




Fig. 134. Diagram showing transition from residual soil into the solid rock 
beneath. 

The uppermost part of the mantle rock, which serves as a source 
of food for plants, is called soil. It varies in thickness from two or 
three inches to as many feet. Locally, it is much thicker. Soil con- 
sists of small particles of minerals, usually mixed with partly decayed 
vegetable matter (humus). Both mineral and organic matter are 
necessary parts of a good soil, but their proportions vary greatly. 
The former is the more abundant in most cases. In color, soil may 

257 



?58 



ELEMENTS OF GEOGRAPHY 



be yellow, dull red, gray, brown, or even black when much humus is 

present. It may be either clayey and compact, or sandy and porous. 

In order to support plant life, soil must contain both air and water. 

Air always is present in sufficient amount, unless crowded out by 




Fig. 135. Igneous rock; the upper Yosemite Falls. 



excess of water, as in the case of certain swamp soils. On the other 
hand, the necessary amount of water may be lacking, as in deserts. 
Such soils are barren, even though perfect from the physical and 
chemical standpoints. In western United States, large areas of 
barren land need only water to be of great value agriculturally. 

In excavations, as for cellars, wells, railway grades, and the like, 



MATERIALS OF THE LAND— THEIR USES 259 

it may be seen that soil grades down in many places into material 
which, though loose, is different in color and texture from the soil 
above. This is the subsoil. In most places the subsoil is much thicker 
than the soil, though it may be absent. (How does the amount of 
humus in the subsoil compare with that in most soils?) 

Solid rock. Beneath the subsoil is solid rock (Fig. 134), which 
extends down to the lowest accessible depths, and doubtless far 
beyond, probably even to the center of the earth. 




Fig. 136. Stratified rocks; bank of Wisconsin River, below Kilbourn. 

Classes of solid rock. Rocks differ in many ways. Their 
particles are of different kinds, sizes, and shapes. Some rocks are 
cemented slightly, others firmly. Some are arranged in layers, others 
are not. Since these and other differences are largely the result of 
the different ways in which the rocks were formed, they have been 
classified on the basis of origin. (1) Rocks formed by the solidifica- 
tion of lavas are igneous rocks (Fig. 135), of which granite is an example. 
(2) Rocks formed by the consolidation of sediments are sedimentary 
rocks. Since in most cases the latter are arranged in layers or strata, 
they are called also stratified rocks (Fig. 136). Conglomerate (cement- 
ed gravel), sandstone (cemented sand), shale (solidified clay), and 
limestone (in most cases the cemented remains of the shells or other 
secretions of animals) are the common sedimentary rocks. (3) When 



260 



ELEMENTS OF GEOGRAPHY 



the character of an igneous or sedimentary rock is changed greatly, 
it becomes a metamor phic rock (Fig. 137; metamorphic= changed). 
In interior United States, solid rocks may be seen chiefly in quar- 
ries, mines, along the courses of certain rivers, and in a few other 
situations; but in eastern Canada, in western Scandinavia, among high 




Fit 



Met amorphic rock. (Ells, Can. Geo!. Surv.) 



mountains generally, and in many other places, they come to the 
surface over large areas. Such places have little value from the 
standpoint of agriculture, even though other conditions are favorable. 



Soils 

Importance to man. Man depends, directly or indirectly, on 
soil for most of that which he eats and wears. Products of the soil 
furnish the principal articles of commerce, and its cultivation con- 
stitutes the chief basis of civilization. These relations, too, are last- 
ing ones. Whether the United States shall in the future contain a 
numerous, well-to-do, progressive population, or a sparse, under-fed, 
and non-progressive one, is largely a question of whether the soil of 



MATERIALS OF THE LAND — THEIR USES 261 

the country is maintained in amount and fertility. In 1900, 35.7 per 
cent of the wage earners of the United States were employed in 
farming. 

The Making of Soils 

We have seen that most soils are formed by the decay and break- 
ing up of solid rocks. All changes which make solid rock crumble are 
processes of weathering. The weathering of rock prepares it for 
transportation by wind and water. 

Chemical processes. The oxygen, carbon dioxide, and water 
vapor of the atmosphere are active chemically. The meaning of 
chemical action is illustrated by the rusting of iron. Iron rust is 
composed of iron, oxygen, and water. Oxygen and water from the 
air enter into chemical combination with the iron. While all three 
of these substances are in the rust, the rust does not look or in any 
way seem like any one of them. The union of oxygen with any other 
substance, as iron, is oxidation. The union of water with another sub- 
stance is hydration. Iron rust is therefore oxidized and hydrated iron. 

The union of oxygen and water with iron increases its volume, and 
the pressure which results causes crumbling. If rusting is allowed 
to continue, the iron is soon " eaten away " entirely; that is, it crumbles 
to pieces. In this case, as in many others, chemical change produces 
physical change. Because it is " eaten away " (weathered) by rusting, 
it is important to keep iron, such as that used in bridges, fences, cars, 
etc., protected by paint. All igneous and most.metamorphic rocks 
contain iron which may be oxidized and hydrated. When these 
rocks are exposed to the air, therefore, the iron in them is changed 
(rusted), and this tends to make the rock crumble. Other chemical 
changes tend to produce the same result. Iron is present in all soils, 
and the yellowish red color of many soils and subsoils is due to the 
oxidized and hydrated condition of their iron. Some of the sub- 
stances made by chemical changes in the rocks are soluble, and if 
they are dissolved and carried away by waters passing through the 
rock, their subtraction makes the latter more porous, and thereby 
weakens it. Some rock-making minerals are soluble without chemical 
change, so that solution is one of the most important means by which 
rocks are made to crumble, and by which soils are formed. 

Mechanical processes. (1) When water freezes, it expands about 
one-tenth of its volume, and in doing so exerts great force. When 
it freezes in rock cavities which it nearly fills, it acts like a wedge, 



I 



262 



ELEMENTS OF GEOGRAPHY 



and may pry the rock apart and break off pieces. This process of 
rock-breaking is most important when there is abundant moisture, 
and where the changes of temperature above and below the freezing 
point of water are frequent. (In what latitudes is the process most 
important? At what altitudes near the equator?) 

(2) When solid rock has no covering of loose material, as on many 
steep slopes, it is heated by day and cooled by night. At high alti- 
tudes, and especially 
on slopes and cliffs ex- 
posed to the noonday 
sun, the daily changes 
in the temperature of 
the surface of the rock 
are great. Rocks ex- 
pand when heated and 
contract when cooled. 
Since they are poor 
conductors of heat, it 
is their surfaces which 
are affected first, and 
most, by changes in 
temperature. Under 
the daily heating and 
cooling, the surface 
part of the rock breaks 

and scales off (Fig. 138). The breaking of cold glass when touched 
with hot water, or of hot glass when touched with cold water, involves 
the same principle. The shattering of rock by heating and cooling is 
very common, particularly in high mountains. Thus the upper part 
of many a mountain is covered with broken rock, so insecure that a 
step may loosen many pieces and start them down the mountain 
(Fig. 139). Great piles of such debris (called talus) bury the bases 
of some mountains to the depth of hundreds of feet (Fig. 140). Pieces 
of talus range from tiny bits to masses weighing tons. They tend 
to decay, gradually forming soil, after which, if other conditions are 
favorable, the slope is occupied by plant life. Changes in tempera- 
ture not only break rocks directly, but also increase greatly the 
surface exposed to chemical action. 

(3) The growth of roots in cracks in the rocks enlarges the open- 
ings, and so helps to break the rocks (Fig. 141). 




Fig. 138. Surface of bowlder scaling off under 
changes in temperature. (Taff, U. S. Geol. Surv.) 



MATERIALS OF THE LAND— THEIR USES 



263 



(4) Burrowing animals make openings in the ground, and in 
the aggregate bring large quantities of loose material to the sur- 
face, where it is exposed 
to wind and water. 

(5) Rivers wear the 
bottoms and sides of their 
channels, and so help re- 
duce solid rocks to fine 
material. 

(6) Glaciers grind and 
crush masses of rock into 
such fine material that some 
of it is called "rock flour. " 
Much of the mantle rock of 
northeastern United States 
was ground up by ancient 
glaciers (p. 387). 

(7) In many dry re- 
gions, wind-driven sand 
wears exposed rock surfaces and forms large quantities of fine, 
loose material. 




Fig. 139. Summit of Granite Peak, Wa- 
satch Mountains, showing broken character 
of the rock. (Church.) 




Fig. 140. View showing long talus slopes. (Russell, U. S. Geol. Surv.) 



264 



ELEMENTS OF GEOGRAPHY 




Classes of Soils 

In the paragraphs which follow, the term soil is used to include 
the subsoil also, where the distinction between them is not important. 
Soil which remains above the solid rock from which it was formed 
is residual soil (Fig. 134). On the other hand, transported soil has 
been brought from its place of origin to its present position by some 
of the agents (wind, water, or ice) which transport materials on the 

surface of the earth. In general, 
transported soils are richer than 
residual soils (Why?), though this 
is not always the case. 

Residual soils. Any kind of 
rock may decay, and the decayed 
rock, properly weathered, becomes 
soil. Soils derived from igneous 
and metamorphic rocks are in many 
places relatively infertile. In some 
cases they are unproductive be- 
cause they are on lands which are 
high (plateau or mountain) and 
rough. On the other hand, the 
soils of the rich cotton lands of 
India are said to be formed by the decay of igneous rocks, and 
the soils of some of the best wheat lands of the Pacific Northwest 
have been described in the same way. In the latter region, how- 
ever, the rich soils are in part, at least, of loess (p. 265), not of 
decayed igneous rock. Among stratified rocks, most sandstones 
weather into poor soil. Shales produce clay soils of greater average 
fertility, but in some cases they are heavy, and hard to work. 
Limestone soils are, as a class, very fertile, but if their limey con- 
stituents are dissolved out, as they may be, the soil is less fertile. 
Stratified rocks form some high plateaus (as in Arizona) and moun- 
tains (e. g., the Appalachians), but they are the commonest rocks 
beneath plains, and over great areas the soils derived from them are 
on level areas or gentle slopes favorable for cultivation. 

Transported soils. Transported soils are much less uniform in 
composition and texture than residual soils. In many cases they 
represent material gathered from a large area, and are entirely unlike 
the rocks on which they rest. Sediment transported and deposited 



Fig. 141. A tree growing in a 
crack in the rock. The growth of 
the tree widens the crack. Sierra 
Nevada Mountains, California. 






MATERIALS OF THE LAND— THEIR USES 265 

by rivers is alluvium, and soils developed on alluvium are alluvial 
soils. Such soils in the flood-plains and deltas of great rivers, when 
not too wet, are commonly of great fertility. The rich soil of the 
great alluvial fan (p. 361) of the Hwang-ho, in China, supports one of 
the densest populations in the world. Ancient civilizations were 
confined so generally to rich flood-plain soils that the period before 
800 B. C. has been called the Fluvial Period. 

Eolian soils are formed from sand or silt deposited by the wind. 
Eolian deposits cover large areas in various regions (p. 3 15), but while 
the sand is loose, and being blown about, it is hardly soil and offers 
little chance for agriculture. For this reason, part of an extensive 
area of sand-hills in western Nebraska has been set aside for a National 
Forest. It is believed that certain trees which can get along with 
little moisture may be grown here successfully, and that the entire 
sand area may be covered finally with a profitable forest. Large 
areas of land have been reclaimed in this way in the southwestern 
part of France. 

Wind has been concerned in the deposition of loess in certain 
regions. Loess is a loam, of buff or gray color, coarser than clay, and 
finer than sand. Soils formed from loess are very fertile when well 
watered. In parts of China, loess deposits have a thickness of several 
hundred feet. Some of the best farming lands of the Rhine, Danube, 
and other European river basins have loess soils. In our country, 
such soils occur in some parts of the Mississippi Basin, particularly 
along parts of the Mississippi and Missouri rivers. Before the Civil 
War, the counties of Missouri covered with loess contained a larger 
percentage of slaves than most of the rest, and grew large quantities 
of tobacco. The loess-covered counties of eastern and southeastern 
Nebraska produce most of the corn, wheat, oats, and alfalfa grown 
in the state. They are settled more thickly, and have more im- 
provements, than most of the rest of the state. 

Much of the mantle rock of Canada, northern United States, and 
northern Europe, was brought to its present position by the great ice- 
sheets which once covered the region (p. 387). This material is 
called drift. Soil formed from drift varies much in character and 
fertility. Some of it is too sandy and some is too stony, but much of 
it is of excellent quality. Since the glacial drift was made not very 
long ago (as geology reckons time) by the grinding up of rocks of 
many kinds, the soils made from it are likely to contain all the 
mineral elements essential for plant food. 



266 



ELEMENTS OF GEOGRAPHY 



Formation versus Removal 
Relation of gain and loss. It has been estimated that in the 
United States it may take, on the average, 10,000 years to form a 
foot of residual soil (833 years for an inch). Slow as this rate is, it is 
faster than the average rate at which soil is removed by surface 
waters, winds, etc. If soil were removed faster than it is formed, the 
land would in time be without soil, as it is now in some places, espe- 




Fig. 142. View in the Apennine Mountains, near Florence. Shows the shal- 
low, stony soil which remains after the loam has been washed away. By removing 
the slight protective cover of vegetation, the sheep promote further erosion. (Sketch 
from photograph by Willis.) 



dally on steep slopes. With the clearing away of forests and the 
plowing of land for agriculture, the rate of soil erosion was increased 
greatly, and it now exceeds the rate of soil formation over large areas. 
From parts of the Apennine Mountains (Fig. 142), Dalmatia, Pales- 
tine, and China (Fig. 143), where the land had been cultivated for 
centuries, the soil has been washed away, and the land is now barren. 
This shows what must be expected in some parts of this country, if 
soil erosion is not checked. The Mississippi River carries, on the 
average, more than 1,000,000 tons of the richest soil matter per day 
into the Gulf of Mexico. The work performed each year by the 
Missouri River in transporting material toward the sea is estimated to 
be equivalent to 275,000,000,000 ton-miles (a ton-mile is a ton carried 
a mile). All the railroads of the United States carried 236,600,000,000 



MATERIALS OF THE LAND — THEIR USES 



267 



ton-miles of freight in 1907. The annual loss to the country from the 
washing and leaching of soils is estimated at some $500,000,000. 
Although the land even of eastern United States has been cultivated 
but a short time compared with that of Europe, yet nearly 1 1 ,000,000 
acres once farmed have been abandoned. More than one-third of 
this area has been ruined for farming by the erosion of the soih It 



W- 




Fig. 143. View in the western part of the province of Chi-li, China. The 
erosion of the metamorphic rocks has been aided in places by recent deforestation. 
(Willis, Carnegie Institution.) 



has been estimated that the area thus ruined would,* if covered by 
fertile soil, be capable of supporting a population greater than that 
of any one of the twelve least populous states. Doubtless the total 
loss to the country from the ■partial destruction of soil is even greater. 
Nor is this all. (1) The soil carried away may do much harm where 
it is deposited (Fig. 144). (2) Streams which carry much sediment 
deposit some of it in their channels, thus impeding navigation. 
(3) The clogging of river channels also helps to cause floods. (4) Res- 
ervoirs, such as mill-ponds, may be filled with sediment, interfering 
with manufacturing. (5) Streams are polluted, interfering seriously 
with their use as a source of water supply for cities, and compelling 
the maintenance of expensive filtering plants. 



268 



ELEMENTS OF GEOGRAPHY 



Factors controlling soil erosion. Several factors influence the 
rate of soil erosion, (i) It is greater on steep slopes than on gentle 
ones. Lands in the southern Appalachians have been cleared of 
forests and cultivated, where the slopes are so steep that the soil was 




Fig. 144. Land covered with sand. The river has deposited a bed of sand on 
the former flood-plain surface, converting it into a barren sand waste. (Glenn, 
U. S. Geol. Surv.) 

washed away in eight or ten years, and the land abandoned. (2) It 
varies with the amount and distribution of rainfall. The more the 
rainfall and the more rapidly it falls, the more rapid the erosion of 

the soil. The greatest 
storm of a year may 
wash away more soil 
than all the other rains 
of that year. (3) It is 
influenced by the pres- 
ence or absence of 
vegetation, and in the 
case of cultivated land 
by the kind of crop. 
Bare soils, and those 
devoted to widely- 
spaced plants, wash 
faster than grass lands 
and forest lands. (4) 
It is affected by the texture of the mantle rock and solid rock. 
(Which would favor greater wash, compact or porous soil? Com- 
pact or porous material below the soil?) 

Prevention of soil erosion. There are various ways of reducing 
soil erosion. The more important are the following: (1) Deep and 




Fig. 145. Terracing in western North Carolina. 
(Sketch from photograph by N. C. Geol. Surv.) 



MATERIALS OF THE LAND — THEIR USES 269 




Fig. 146. Erosion as result of killing of 
grass by stock. Foothills of Sierra Nevada 
Mountains, California. (Fairbanks.) 



frequent tillage increases the power of the soil to absorb rain, and 
so reduces the amount of water running directly off over the surface. 
This is highly desirable 
apart from its effect on 
erosion, for few places have 
water enough to produce 
maximum crops. (2) 
Plowing and planting along 
contours produce little 
depressions and ridges at 
right angles to the slope. 
These tend to check erosion 
(How?). Plowing up and 
down a slope, on the other 
hand, increases erosion 
(Why?). (3) On steep 
slopes, wash may be re- 
duced by making a series 

of terraces or benches. Terracing is practiced in parts of the Pied- 
mont Plateau (Fig. 145) and elsewhere in the South, and in many 
countries of Europe 
and Asia (p. 475). (4) 
The soil should be kept 
covered with vegeta- 
tion as much as pos- 
sible throughout the 
year. (5) Grasses tend 
to prevent wash in sev- 
eral ways (How? Fig. 
146). (6) On slopes 
exceeding 18 or 20 in 
steepness, the soil is 
protected best by trees 
(Fig. 147), and, in gen- 
eral, such land should 
be devoted to forests. 
The restraint and pre- 
vention of soil erosion 

are among the most important problems of the conservation move- 
ment, and they depend very largely on individual land-owners. 




Fig. 147. View showing effect of roots in hold- 
ing soil. San Juan Mountains, Colorado, near 
Silverton. (Fairbanks.) 



270 ELEMENTS OF GEOGRAPHY 

Mineral Plant Foods 
Proper care of the soil requires not only the prevention of erosion, 
so far as possible, but also the keeping in the soil of the mineral 
matters needful for plant food. The elements essential to plant life 
are phosphorus, potassium, calcium, silicon, carbon, hydrogen, oxy- 
gen, and nitrogen. Several of these elements are derived wholly 
from the soil and from the water in the soil, while others are taken 
from the air. A number of other elements derived from the soil, such 
as sulphur, sodium, and iron, are also used in minute quantities by 
plants. Different crops draw unequally o^i the mineral foods of the 
soil, and when one crop is grown on the same ground year after year, 
the soil becomes poor in one or more of these foods, and its produc- 
tivity is reduced. The almost exclusive cultivation of tobacco in- 
jured the soil in parts of colonial Virginia. This helped to send 
thousands of farmers west of the Appalachian Mountains in search 
of new land. Southern Wisconsin was primarily a wheat region from 
the 1830's to the 1870's, when the diminishing yields and the com- 
petition of the new, rich soils farther northwest forced the cultivation 
of other crops, and the adoption of better methods of farming. 
Where crops of different kinds are raised, one after another (rotation 
of crops), the soil remains in better condition; but unless the essential 
elements taken from the soil by plants are returned in some way, its 
fertility must diminish. "Worn-out" farms are common in the 
South and East, and even in parts of the Upper Mississippi Basin. 
Land may be kept from wearing out by giving it the elements it lacks, 
that is by fertilizing it. In some parts of the southeastern states, 
where the soil was made poor by the long-continued growth of cotton 
or tobacco, no crops are grown without the use of fertilizers. 

Natural processes tend to add to the soil the chemical substances essential 
to plants. New soil is formed by the weathering of underlying rocks (p. 261), 
and ground-waters bring mineral matter in solution from below, which they may 
deposit near the surface, enriching the soil. In most cases, these processes of soil 
renewal and enrichment fail to offset the drain upon the soil imposed by ordinary 
methods of agriculture. While in many places natural processes tend to enrich 
soils, surface and underground waters may also erode (p. 266) and leach soils, 
thereby reducing them in amount and productivity. 

Except phosphorus, the supplies of the elements which plants 
need are abundant from one source or another. Hydrogen and oxy- 
gen are the constituents of water, and oxygen makes one-fifth of the 



MATERIALS OF THE LAND — THEIR USES 271 

atmosphere. Next to oxygen, silicon is the most abundant element 
in the earth's crust. Most rocks contain a little calcium, and limestone 
contains much. Carbon is derived from the carbon dioxide of the air, 
and the latter contains an unlimited supply of nitrogen which may 
be drawn upon by certain plants, though most plants depend on the 
nitrogen compounds in the soil or in fertilizers (p. 47). Potassium 
is a constituent of many common rocks, and, in addition, there are 
large deposits of potassium compounds in various places, especially 
Germany. The compounds of potassium are dissolved readily by 
ground-water, so that soils are likely to become poor in this element. 
Wood ashes contain potassium, and for this reason they are good 
for land. 

Unlike the foregoing, phosphorus is a relatively rare element, and 
already the original amount in the soil has been diminished seriously 
in many parts of the United States. Guano, chiefly from islands off 
the west coast of South America, is an important source of supply, 
though little is imported into the United States. The bones of do- 
mestic animals are a second source, and the manufacture of phosphate 
fertilizer is an important industry at the great slaughtering centers. 
The bones of buffaloes, killed in great numbers years ago, have been 
gathered up by the train-load from the western plains and used in the 
same way. Enormous quantities of phosphorus are now lost in the 
sewage of great cities, and in the leaching of farm manure. This 
phosphorus should be returned to the soil, so far as possible. Some 
European countries are far ahead of the United States in this matter. 
Finally, the United States possesses the greatest known deposits of 
phosphate rock (rock containing much phosphorus), and because 
phosphorus is to be a critical factor in the fertility of soil, these de- 
posits constitute one of the most important mineral possessions of the 
nation. In the Southeast, there are deposits in South Carolina, Flori- 
da, Tennessee, and Arkansas. The first three of these states furnish 
nearly all the phosphate rock now mined in the United States. 
In addition, there are far greater deposits in Idaho, Wyoming, Utah, 
and Montana. There is, unfortunately, much waste of the poorer 
phosphate rock in mining — material which, if saved, would be of 
great value in the future. Unfortunately for the United States, too, 
increasingly large amounts of phosphate are being exported. 

It is not to be inferred from the above discussion that fertility of soil is deter- 
mined solely by its chemical composition. The productivity of soil is influenced 
also by (1) its physical condition (coarseness, fineness, etc.), (2) its water content, 



272 



ELEMENTS OF GEOGRAPHY 



(3) the organic matter (humus, etc.) which it contains, (4) the minute organisms 
(especially bacteria) at work in it, (5) the presence of tcxic bodies (the accumulated 
excreta of plants), and by other factors. Furthermore, the yields obtained from 
a given soil are affected greatly by (1) the quality of seed sown, (2) the effective- 
ness of cultivation, and, in many cases, by such things as (3) harmful insects, (4) 
plant diseases, and (5) weather conditions. The reduced yields of many long- 
cropped soils probably are due in part to causes other than the impoverishment of 
the mineral elements of plant food. 

General Distribution and Use of Soils in the United States 
The principal physiographic provinces of the United States are 
shown in Fig. 148, and the principal soil provinces in Fig. 149. Since 
the settlement and development of these provinces have been influ- 




Fig. 148. Map showing the principal physiographic subdivisions of the 
United States. 

enced profoundly by the configuration of the land and the character 
of the soil, the larger provinces may be considered briefly. 

The Atlantic and Gulf Coastal Plains. The Coastal Plain 
widens southward from New York City, and has its greatest width 
in the Gulf region, whence it extends northward along the Mississippi 
to the mouth of the Ohio. Much of the Coastal Plain is less than 
100 feet above sea-level, though some parts of it are considerably 
higher. The underlying rocks are imperfectly cemented gravels, 
sands, clays, marls, and limestones. Along the coast there are 
extensive marshes, where most of the soil is too wet for cultivation. 



MATERIALS OF THE LAND— THEIR USES 273 



The draining of these swamps has been begun, as for example on the 
delta and lower flood-plain of the Mississippi, and when it is com- 
pleted their rich soils will support a dense farming population (p. 460). 
Elsewhere, the soils of the Coastal Plain present great variety. 
Over the marls and limestones they are fertile, and over the sands, 
gravels, and clays they are much less productive. Many sandy 
tracts, as in parts of southern New Jersey, have remained wooded 




Fig. 149. Map showing the principal soil provinces of the United States. 
(After Whitney, with slight modifications.) 

and sparsely settled to the present. In the Carolinas such belts, 
called "barrens," long helped to separate the life of the tidewater 
country from that of the Piedmont Plateau. In contrast with the 
sandy areas, the bottom lands of the rivers, where not too wet, and 
the belts of limestone soils are the garden spots of the South. Here 
most cotton was grown before the Civil War, and most slaves were 
owned (p. 492). Here the negro population is densest to-day. It 
is probably true that the rich soils of many parts of the Coastal Plain, 
and the genial climate of the South, were responsible for the continu- 
ance of slavery in the United States to the time of the Civil War. 

The New England Hills. There is no continuous Coastal Plain 
in New England. The most important lowlands have developed on 
weak rocks in the Connecticut Valley, about Narragansett Bay, and 



274 



ELEMENTS OF GEOGRAPHY 



around Boston. On these lowlands the early history of Connecticut, 
Rhode Island, and Massachusetts centered. To-day, the Boston Basin 
contains about half the people of Massachusetts, and one-fourth those 
of all New England. Apart from these lowlands, most of New England 
is hilly. Much of its glacial soil is thin and poor, and in many places 
stony (Fig. 150). It has been estimated that in some parts it took, 
on the average, one month for a man to remove the stones from each 
acre of glacial drift, to get it ready for farming. Many of the early 
settlements were made in areas of stratified drift (p. 407), where the 
bowlders were fewer and the land flatter. 

The unfavorable soils and the harsh climate prevented a high 
development of agriculture in New England, which was without a 




Fig. 150. A bowlder-strewn surface in Maine. 



single staple crop for export, such as colonial Virginia had in tobacco, 
and South Carolina in rice and indigo. By the close of the seventeenth 
century, more than half the people of New England were engaged in 
industries other than agriculture, and it is said also that more than 
half the time of the farmers was given to non-agricultural work. For 
two centuries the life of New England was dominated by industries 
centering in the ocean, — chiefly fishing, shipbuilding, and the carrying 
trade. Later, manufacturing became the leading interest. 

Crude methods of agriculture in early days led to the exhaustion 
or partial exhaustion of such lands as were originally good for farm- 
ing. When the lands ceased to produce good crops they were desert- 
ed, and much has been written and said of the abandoned farms of 
New England. But in recent years many of these farms have been 
brought under cultivation again, and with the improved methods of 
to-day they are producing satisfactory returns. It seems certain 



MATERIALS OF THE LAND— THEIR USES 275 

that many of the abandoned farms here will be reclaimed. Much 
of the rough, infertile upland of New England, however, probably 
can be used to best advantage in the future for forests. 

The Piedmont Plateau. The Piedmont Plateau has an eleva- 
tion varying from 250 or 300 feet at its eastern edge, to about 1,000 
feet in places along its western margin. It is underlain for the most 
part by crystalline (metamorphic and igneous, p. 259) rocks. The 
higher lands have a rather poor, residual soil, but many of the valleys 
have rich, alluvial bottoms. 

The Appalachian Mountains. The Appalachian Mountains 
consist of both sedimentary and crystalline rocks. The soils of the 
larger valleys are fairly fertile. This was strikingly true, originally, 
of the limestone soils of the Great Appalachian Valley, which, under 
various names, extends from Georgia to New York. This great 
valley was one of the first areas west of the Blue Ridge to be settled, 
and it soon became an important grain-producing section. During 
the Civil War, the Confederate armies drew large quantities of sup- 
plies from its fertile fields. 

The upper slopes of the mountains are steep, and covered with 
poor soil which washes easily when the forest is removed. A National 
Forest is to be established in the southern Appalachians, and the 
steeper land devoted permanently to forestry. In the future, the 
country must look to the Appalachian forests for much of its supply 
of hardwood. 

The Cumberland-Alleghany Plateau. The surface of this plateau 
is much dissected by valleys cut in the nearly horizontal, stratified 
rocks. In general, relatively level land and fertile soil are found 
only in the valley bottoms. The hills have steep slopes, and their 
soils are infertile. Except where mineral resources have attracted 
settlers, the plateau is sparsely settled. 

Lake and Prairie Plains. Most of this area is underlain by 
sedimentary rock, much of which is limestone. Most of the surface 
is covered with glacial soil (Fig. 149), the composition of which is 
influenced greatly by the nature of the underlying rocks. Thus 
in Michigan and Wisconsin there are extensive areas of sandy drift 
over sandstone, where attempts at farming, following the removal of 
the pine forests, have met with little success. There are also hilly 
belts (moraines, p. 395) in the northern part of the area, where the 
stony soil is used largely for woodlots and pasturage. There is also 
much marsh land, unfit for agriculture until drained. In general, 



276 ELEMENTS OF GEOGRAPHY 

however, the soils of this region, especially the prairie soils between 
the Missouri and Ohio rivers on the south and southwest, and the 
Great Lakes on the north, are of great fertility. No other equal 
area in the United States is so important agriculturally (Fig. 402). 
Iowa, Illinois, Ohio, and Indiana are, in the order named, the first 
four states in the percentage of improved land to total area. 

The prairies generally were avoided by the first settlers, who 
regarded the absence of trees as evidence of poor soil. Even after 
their fertility was known, the larger prairies were not settled far back 
from the main streams until the building of railroads provided means 
of transportation. 

The Great Plains. The surface of this province rises from 
an elevation of about 1,000 feet at the east, to more than 5,000 feet . 
at the west. Most of the region is underlain by sedimentary rocks, 
and, in general, has a deep and rich soil. At the north, the soil is of 
glacial origin (Fig. 149); farther south it is (1) partly alluvial, having 
been spread widely by depositing rivers flowing eastward from the 
Rocky Mountains, (2) partly residual, and (3) considerable areas in 
the eastern part of the tract are covered with loess (p. 265). The 
eastern part of the area is very productive, but in the western part the 
rainfall is too scanty for ordinary farming. Here agriculture must 
depend on (1) irrigation, which is possible over small areas, (2) "dry 
farming" (p. 498), and (3) the cultivation of drought-resisting plants, 
such as durum wheat and kaffir corn. Over large areas grazing prob- 
ably will continue to be the dominant interest (p. 49S). 

The Rocky Mountains and Western Plateaus. In the dif- 
ferent parts of this great region all kinds of rocks are found, in 
all sorts of positions. The soils vary as greatly as the rocks, both 
in origin and composition. Glacial soils are found at the north, and 
throughout the region in many mountain valleys. Great areas of 
alluvial soil fringe the bases of many of the mountains, where wither- 
ing streams from the uplands have deposited their sediment. Some 
of these deposits have a thickness of hundreds and even thousands 
of feet. The steep slopes are flanked also by great piles of talus 
(p. 262), most of which do not support much plant life. Where the 
mountain slopes are not too steep, there are residual soils, and these 
also cover great areas of the plateaus. 

Over most of the region, systematic tillage of the soil has not been 
possible because of (1) too great height, (2) the steepness of the slopes, 
or (3) lack of adequate rain. Most of the land is therefore best suited 



MATERIALS OF THE LAND — THEIR USES 277 

to grazing, and, especially in the mountains, to forestry. Irrigation 
is making agriculture of a high order possible in many rather small 
areas (p. 449), especially in valleys and on other lowlands. In some 
such places, there is a dense population. Nowhere else in the world 
is ffuit-raising carried on more intelligently or with better results, 




^~ 



RELET MAP 

or 
CALIFORNIA 



■. 






. \r~--% ■^:4^si'-"*;'-V---"? i N 







Fig. 151. Relief map of California. The state is largely mountainous, but 
the central plain is conspicuous. 



and probably nowhere else in the world has farm land sold at such 
high prices. Small, choice orchards have been sold at $4,000 and 
$5,000 per acre, and prices half as high are not rare. 

The Pacific Ranges. The Sierra Nevada and Cascade ranges 
on the east, and the coast ranges, at the west, are composed largely, 
but by no means wholly, of crystalline rocks. As farther east, the 
soils of the mountain slopes can be used best for forests, for which, 
except at the south, there is sufficient rain. Among the mountains 
there are many fertile valleys with glacial or alluvial soils, and 



278 ELEMENTS OF GEOGRAPHY 

between the ranges are the "great waste-filled valleys of the Willamette 
River and of central California (Fig. 151). The rich, alluvial soils 
of the latter probably have given the state larger returns than its 
gold mines. In the southern part of the province, the value of even 
the best soil depends on irrigation, and unfortunately there is w'ater 
enough to irrigate only about one-tenth of the land. Irrigated land, 
with groves of oranges or lemons, sells for very high prices, while non- 
irrigable land may in many places be bought for a trifle. Toward the 
north, with increase of rainfall, and with lower temperatures, the 
necessity of irrigation is less. The Willamette, Rogue, and Hood 
river valleys of Oregon, as well as extensive tracts in Washington, 
yield good crops without irrigation. But even here irrigation in- 
creases the returns from the land. 

Fig. 152 shows, in a general way, the best use to which it is 
thought the land throughout North America may be put, and serves 
to illustrate many of the larger points stated in the preceding 
paragraphs. 

Mineral Products and Their Uses 
Building Stones and Clay 

Building stones. The principal building stones are granite, 
limestone, marble, slate, and sandstone, though not all rocks of these 
kinds are useful for building. The strength of the rock, its color, ease 
of splitting and dressing, and durability all enter into the problem. 
Not all good stone is available, for much is too far from a market. 

Granite is distributed widely in the United States. Granite and 
other similar rocks form the cores of many mountains, especially in 
the West, and are the surface rocks over large areas in the Piedmont 
and New England plateaus, and in the vicinity of the upper Great 
Lakes. Granite has been quarried in a large way for many years in 
New England, and more than two-thirds of all granite quarried 
in the country comes from the Atlantic States (Why?). 

Limestone is quarried in many states, largely for local use. From 
a few famous quarries, such as those at Bedford, Indiana, it is shipped 
to all parts of the United States. Much limestone is burned for lime, 
and much is used for mortar, cement, railroad ballast, etc. In the 
making of cement, lime is mixed with clay. The recent development 
of the cement industry has been remarkably rapid. In 1890, the 
United States produced less than 350,000 barrels of Portland cement; 
in 1910, more than 76,500,000 barrels. 



MATERIALS OF THE LAND— THEIR USES 



279 



Much marble (metamorphic limestone) is used as an ornamental 
building stone. It is white if formed from pure limestone, but 
because of impurities may be of any color. Carbon and other im- 
purities often form streaks or bands of varying color, producing beau- 




LEGEND 

19% W%& Absolute Forest Land 

hermediate between Agricultural 
and Forest Land 
Sw ill Agricultural Land 
26* ^^ Grazing Land 
?.« LZn Barren La'nd 
100% Total 



Fig. 152. Map showing the best use to which it is thought the land through- 
out North America may be put. (Zon, U. S. Forest Service.) 



', 



280 ELEMENTS OF GEOGRAPHY 

tiful and odd effects on polished surfaces. Marble is quarried on a 
large scale only in the East. Vermont supplies about four-fifths of 
all the marble used in the United States for ornamental work, but 
Colorado promises to become a great producer. 

Slates are metamorphic rocks formed from shale by great pressure. 
They are used chiefly as roofing material, but also .for various other 
purposes. The production of slate, like that of marble, is confined 
largely to the East, and is most important in Pennsylvania, Vermont, 
and New York. 

Sandstone is used for buildings, bridges, and other purposes. It is 
distributed widely in many states, so that numerous small quarries 
serve local needs. A few popular kinds of sandstone, such as the 
brownstone from Pennsylvania and the vicinity of New York City, 
have wider markets. 

Gypsum is used extensively for building plaster and certain 
cements. It is also used as a land fertilizer, and in other ways. 
Great deposits of it occur in some states. 

Clays and clay products. Clays have a wider distribution 
than most other economic rock materials, and are used in making 
many things. Among these are pottery of various grades, tiles, 
terra cotta, brick, and Portland cement (made from a mixture of 
clay and lime rock). Every state produces clay products, Ohio, 
Pennsylvania, New Jersey, and Illinois leading in the order named. 
The total value of the products of the clay-working industries of the 
country exceeded $170,000,000 in 1910. 

Substitution of mineral products for wood products. Brick, 
stone, and cement are being substituted more and more for wood in 
building operations. This is highly desirable, because these materials 
are (1) more durable, (2) less liable to fire, and (3) their use lessens 
the drain on the forests. Wood was used in only 27.5 per cent (by 
cost) of the building operations in the 128 leading cities of the United 
States in 1909. Operations on brick buildings constituted 61.49 per 
cent of the entire cost. On the other hand, wood continues to be 
used much more than other materials in most of the smaller towns 
and villages, and in the country. 

Mineral Fuels 
Coal. After soil, coal is the most important of the mineral 
resources. Together with iron, which is next in importance, it has 
made possible the extraordinary industrial development of the 



I 



i 



MATERIALS OF THE LAND — THEIR USES 281 

United States. Germany and England also have become great manu- 
facturing nations, largely because of their extensive deposits of coal 
and iron. The United States has more and better coal than any other 
country, so far as now known. Fig. 153 shows the general distribu- 
tion of its coal fields. Their combined area is about 500,000 square 
miles, or about 16 per cent of the area of the country. They are 
distributed widely, a matter of great importance, since the cost of 





^w 














J(\J) 




Jr ' 


I ( Y 




^K — r 


-^_/TV 


3^3-^ 
























V * \ 


[&££_ 


1 * 








S 


'•Jx 




' 


y *m ^B 




— 1 f 










/ »' * 


-J 


Pfk£ 






^SWBMk KNOWN COAL 

FIELDS 

m DOUBTFUL 

. CO/U FIELDS 

\ 1-' 1 CO/)t UNDER 

\ DEEP COVER 



Fig. 153. Map showing general distribution of coal fields in the United States. 
(U. S. Geol. Surv.) 



coal is largely the cost of transportation. The total amount of coal 
in the United States at the beginning of 1908 was estimated at more 
than 3,076,200,000,000 tons. About one-third of this, however, 
is accessible only with difficulty, and by no means all of it is 
of good quality. It is estimated that more than 99 per cent 
of the original supply of coal in the United States is still in the 
ground. 

The mining of coal in the United States began to be important 
about the middle of the last century, and the output has nearly 
doubled each decade since. The 501,000,000 tons mined in 1910 
constituted about Vie of all mined to the end of that year. If the 
output should continue to increase at the same rate, the entire known 
supply would be exhausted in less than 150 years. For various 



282 



ELEMENTS OF GEOGRAPHY 



reasons, however, our supply of coal will last much longer than this. 
Nevertheless, it is highly desirable (i) to avoid, so far as possible, 
the waste of coal; (2) to substitute water power for steam power 
(generated by the burning of coal) wherever practicable; and (3) to use 
coal in the most efficient way possible. The waste in mining coal 
has amounted to about 50 per cent of the quantity produced; that 
is, about 250,000,000 tons were wasted in this way in 1910. This is 
more coal than was mined in the United Kingdom (the second coal- 




Fig. 154. Digging peat in Ireland. 



producing country) in 1905. Much unburned coal passes off as 
smoke (p. 51). The average steam engine does not develop into 
power more than 6 to 10 per cent of the heat energy of the coal. 
In making light from coal, only a small part of one per cent of the 
energy of the coal is utilized. Much of this waste can be avoided, 
and some progress in this direction has been made already. One 
effect of the burning of large quantities of coal is to increase rapidly 
the amount of CO2 in the air (p. 48). Indeed, it has been estimated 
that the amount may be doubled in this way in the next 1,500 years. 
It will be remembered (p. 50) that this probably would make the 
climate much milder. 

Pennsylvania, West Virginia, Illinois, and Ohio lead in mining 
coal. They have produced about ^ of all the coal mined in the 
United States. 



MATERIALS OF THE LAND— THEIR USES 



283 



Peat. Though not a mineral fuel, peat is best mentioned in 
connection with coal. Peat is a swamp deposit, much of it resulting 
from the partial decay of a moss called sphagnum. In the United 
States more than 11,000 square miles, outside of Alaska, are estimated 
to have peat beds of good quality, containing a total of nearly 13,000,- 
000,000 tons of fuel when dried. The largest deposits are in the 
glaciated area (Fig. 273), along the Atlantic and Gulf coasts, in the 
Mississippi delta, and along the flood-plains of the Mississippi and 
certain of its larger tributaries. These great peat deposits scarcely 
have been touched, but the extensive use of peat in northern Europe 
suggests its future importance here. There it has been used for many 
years as fuel (Fig. 154), especially in Ireland, and recently in a variety 
of other ways, such as for making coke, charcoal, illuminating gas, 
fertilizers, and paper. 




Fig. 155. Map showing general distribution of petroleum and natural gas 
fields of United States. (Day, U. S. Geol. Surv.) 



Petroleum. The distribution of the known supplies of petroleum 
is shown in Fig. 155. 

Petroleum was discovered in large quantities in western Pennsyl- 
vania in 1859. The field which includes this original area extends 
from New York to Tennessee, and has produced more petroleum than 
any other. The output is now decreasing, however. Most of the 



284 ELEMENTS OF GEOGRAPHY 

petroleum of this field is of high grade. The large Ohio-Indiana field 
was the second to come into use (about 1885). Most of the others 
are of recent development. In 19 10, California produced most 
petroleum, and Oklahoma and Illinois ranked second and third. The 
total output of the country was more than 200,000,000 barrels. Since 
i860, as much petroleum has been produced each nine years as in all 
preceding years, and should this rate continue, the supply, so far as it 
can be estimated in known fields, would be exhausted by about 1935. 
Should the present output continue without increase, the calculated 
supply will last until about the year 2000. 

Crude oil is used for fuel, for the prevention of dust on roads, and 
for some other purposes. From it various oils are manufactured 
for lighting and lubricating purposes, and many by-products are 
obtained. In view of the probable early exhaustion of the supply, 
petroleum should be used only for those purposes for which it is 
best adapted. Its most essential use is for the making of oils for 
lubricating the bearings of all kinds of machinery. For this purpose, 
no satisfactory substitute is known. On the other hand, the use of 
petroleum as fuel in locomotives and for the development of power 
in factories is in general unnecessary, and should be discouraged. 

Natural gas. Natural gas is the most perfect fuel. So far as 
known, the United States has a greater supply than any other nation, 
and it occurs in more than half the states (Fig. 155). It is believed, 
however, that the natural gas now known will be exhausted within 
the next twenty-five or thirty years. In spite of this, and in spite of 
its great value, enormous quantities (estimated at 1,000,000,000 
cubic feet daily) are allowed to escape from the ground unused. A 
large part of this waste can be prevented. 

The opening up of new gas and oil fields has been attended in- 
variably by a great local increase in land values, and in some cases 
has started a period of great industrial activity (p. 570). Where 
wells have failed later, a period of stagnation and decline has in some 
cases followed. 

Metals 

Iron. Some iron was mined in this country early in the colonial 
period. In eastern Massachusetts, for example, it was taken from 
certain marshes, ponds, and lakes, and used in local manufacturing. 
The production was unimportant, however, till 1850. Since then it 
has increased rapidly, so that the output during the decade ending 



MATERIALS OF THE LAND — THEIR USES 



285 



with 1909 amounted to 52.6 per cent of all the iron ore that has 
been mined in the United States. 

It was estimated recently that the available iron ore (that usable 
under existing conditions) in the United States amounts to nearly 
4,800,000,000 long tons (a long ton is 2,240 lbs.), and that in addition 
there are low grade ores, part or all of which will be useful in the future, 
amounting to more than 75,000,000,000 long tons. Like coal, iron 



N kJfc-»^_ 








1 • l~l — . 








•/V \ . r 1 


/CLthT^ 


'"X-^- 


y^ 


? -s^\\y[ 


\ ' \j $ .' ,'/' h—r— LlJ_ 


A ' l{ 




kT^r 


\t% \ • / I , 1 


1 "^xJ 


*jf* ^/^ 




v- "\ 'k~-~~~l2^- 1 


x-"' "i ' J~ •' 1 — 1 




L—J0< 




m\* j 







Fig. 156. Map showing general distribution of iron ore in the United States. 



ore is distributed widely (Fig. 156), but by far the most important 
deposits of our country are in the Lake Superior region, especially 
in northern Michigan and Minnesota. This district contains about 
73 per cent of the available ore of the United States, and about 95 
per cent of the low-grade reserve. It had produced, to the end of 
1910, nearly 500,000,000 long tons of iron ore — considerably more 
than half the total amount produced in the United States. In recent 
years it has furnished about 80 per cent of the entire output of the 
country. In 1910, the United States produced more than 56,800,000 
long tons of iron ore — nearly half the world's production for the year. 
If the iron ores of the United States continue to be mined at the 
increasing rate of the last few decades, the known deposits of high 
grade will all be mined in about ninety years. Several considerations, 
however, make it certain that the supply of ore will last much longer. 



286 ELEMENTS OF GEOGRAPHY 

Furthermore, iron, unlike coal, can be used again and again. For 
example, old rails are made over into new ones or into other things. 
The great problem in conserving the supply of iron is therefore to 
use it again and again, keeping the stock as nearly intact as possible. 
There is little waste of iron ore in mining. 

Copper. The existence of copper on the southern shore of 
Lake Superior (Keweenaw Point) was known to the Indians at an 
early date. As late as 1845, however, the entire output in the United 
States amounted to only 100 tons a year, and not till 1867 did copper 
begin to be used in large amounts. Its use has increased rapidly in 
recent years, and in 19 10 approximately 540,000 tons were produced. 
Nearly three-fifths of the entire amount produced in the United 
States have been extracted during the last ten years. Michigan, 
long the leading copper state, is now out-ranked by Arizona and 
Montana. Some nine other states, most of them in the West, produce 
copper, several of them in large amounts. 

Copper ores are scattered so widely, and are so irregular in their 
occurrence, that the supply has not been estimated accurately. 
It is thought, however, that the known reserves of copper ore, 
usable at existing prices, will be exhausted in Michigan in fifteeen or 
twenty years, and in Montana and Arizona in even less time. Should 
the value of copper increase, lower grade ore could be used. Even 
now, at the Michigan mines, only twenty-two pounds of copper 
are obtained, on the average, from each ton of ore. New discov- 
eries of copper are being made from time to time. For these and 
other reasons, the deposits will last much longer than the time sug- 
gested above. 

Copper is used chiefly for making wire and brass. Fortunately, 
these uses involve little unavoidable waste, so that the same cop- 
per may be used repeatedly. Some copper is used for chemical 
purposes. 

Gold. The production of gold was unimportant in the United 
States until after its discovery in California in 1848. The lead- 
ing gold-producing states are Colorado, California, and Nevada. 
Each produces about 1,000,000 ounces (an ounce is worth about 
$20) of gold per year. Alaska is also a heavy producer. The amount 
of gold which remains to be mined cannot be estimated, nor, in 
consequence, the duration of the deposits. It already is practi- 
cable to mine very low grade ore. In some cases, for example, 
a ton of ore is mined and milled to recover one-eighth of an ounce 



\ 



MATERIALS OF THE LAND — THEIR USES 287 

of gold. Gold is used chiefly as coin and bullion, and in the arts. 
Most of its uses involve little waste or loss of the gold itself. Even 
were the supply used up, the loss would be much less serious than 
that of coal or iron. 

Silver. Neither the amount nor the future life of the silver 
deposits of the United States can be estimated. Nevada, Montana, 
and Utah are (1910) the leading silver-producing states, followed 
by Colorado and Idaho. Like gold, silver is used chiefly for coin and 
in the arts. Its use in photography is an interesting and a rapidly 
increasing one. In general, there is little waste or loss in its use. 

Lead and zinc. Lead was known to the Indians of the Missis- 
sippi Valley before the coming of the whites, but the deposits of 
the region were not worked effectively, until the early 1820's, when 
a period of great activity in mining began. This culminated in 
Illinois and Wisconsin about 1845, and during the next few years 
many of the miners went to the new iron fields of Lake Superior, 
and to the gold fields of California. Lead was discovered later in 
a number of the western states, in many places in association with 
silver. Missouri is the leading lead-producing state, followed by 
Idaho and Utah. 

Lead is another metal the amount and duration of which cannot 
be estimated accurately. The known supply is, however, very lim- 
ited. Much lead is lost needlessly by the current methods of mining, 
milling, and smelting. About one-third of the lead produced in 
the United States is used in the manufacture of paint. Lead used 
in paint can be used but once, and more abundant things will have 
to be substituted for it increasingly in the future. 

Zinc is associated in many places with lead, and for years was 
regarded as valueless by lead miners. The first zinc plants were 
erected in Illinois in the late 1850's, but for twenty years the pro- 
duction was small. In recent years it has increased very fast, and 
the output of the last decade equalled that of all earlier years. 
Missouri leads, by a large margin, in the production of zinc. There 
is great waste of zinc in mining, concentrating, and smelting. About 
two-thirds of that produced in this country is used for galvanizing 
iron. Like lead, it is used also for making paint. Most of the rest 
is used (with copper) for making brass, and for sheet zinc. 

Aluminum. Aluminum is by far the most abundant of the 
metals. It is a constituent of all important rocks except limestone 
and sandstone, and makes up more than 8 per cent of the earth's 



288 ELEMENTS OF GEOGRAPHY 

crust. It is light, strong, malleable, ductile, is a good conductor of 
electricity, takes and retains a high polish, and does not corrode 
easily. These properties fit it for many purposes, but the diffi- 
culty and expense of separating the metal from its combinations 
long prevented its extensive use. It is extracted on a commercial 
scale only from bauxite, a relatively scarce mineral. When it can be 
obtained cheaply from clay, of which it forms a part, its use will 
be increased enormously. 

The production of aluminum in the United States increased from 
83 pounds in 1883 to more than 47,000,000 pounds in 1910. It 
is used for making a constantly increasing variety of things, such 
as cooking utensils, castings, wall "paper," ceiling panels, paints, 
varnishes, and wire. Doubtless in the future it will replace iron, 
copper, and some of the other metals for many purposes. 

Salt 
Salt is indispensable to man, and fortunately the supply is prac- 
tically inexhaustible. (1) In arid regions there are many lakes 
with no outlets into which streams bring minerals (including com- 
mon salt) which have been dissolved during the passage of the water 
through or over the rocks (p. 330). These things are left behind as 
water evaporates from the surface of the lake, which becomes more 
and more saline as the process continues. When the waters of the 
lake become saturated, further evaporation causes the minerals 
to begin to be precipitated from solution. Great Salt Lake is 
estimated to contain some 400,000,000 tons of common salt. 
(2) Extensive salt beds which were laid down in ancient lakes or 
arms of the sea are found between beds of other rock in many places. 
Those in central New York may have an area underground of some 
10,000 square miles (larger than Vermont), and single beds are in 
places 80 feet thick. Beside New York, Michigan and Kansas are 
leading salt-producing states. (3) The ocean constitutes the remain- 
ing and greatest source of supply (p. 235). 

The need of salt helped to hold most of the American colonists near the 
Atlantic coast for a long time. Not until it was discovered in the Holston and 
Kanawha valleys (Tenn. and W. Va.), in central New York, and in Kentucky, 
did dependence on the coast for salt cease. In 1778, salt brought on pack animals 
over the Appalachian Mountains sold in southwestern Pennsylvania for £6 10s. 
per bushel. The same amount of salt now is worth but little more than 10 cents 
where it is prepared, and not more than 50 cents in the markets in most parts of 
the United States. 



MATERIALS OF THE LAND— THEIR USES 



Conservation of Mineral Resources 

The mineral resources noted above are a part of the heritage 
of the earth. The people of to-day have a right to use such of them 
as they need, in as great quantities as necessary. It is their duty, 
however, to use them in such a way as to insure the minimum of 
waste and the maximum of efficiency. This is demanded alike 
by the interests of the present generation, and by those of genera- 
tions to come. The facts given show that many reforms are needed. 
The reckless waste of some of these resources is a reflection upon 
American intelligence. 

Questions 

i. Does the absence of soil in any given place mean that it is not in process 
of formation there? Explain. 

2. Is the breaking of rocks by expansion and contraction most important 
at high or at low altitudes ? In high, middle, or low latitudes? In moist or dry 
climates ? Why ? 

3. What are the principal ways in which soil is being formed in New England? 
Florida? Nevada? 

4. Why are the soils of the lower flood-plains and deltas of large rivers of great 
fertility in most cases? Are they commonly of coarse or fine texture? Why? 

5. Enumerate the conditions (all of them) which may explain the fact that 
soil wash is, in some cases, much faster on one of two equal slopes than on the 
other. 

6. In general, would you expect wash in winter from bare fields to be greater 
in northern or southern United States? Why? 

7. Would it be desirable, from the standpoint of agriculture, entirely to 
prevent, if possible, soil erosion? Reasons? 

8. Tile underdraining is in many cases effective in checking soil erosion. 
Why? 

9. Plowing under straw, leaves, etc., was formerly a common practice. What 
value, if any, would this have? 

10. In some of the mountainous areas of Italy, Austria, and other countries, 
forests are maintained in strips at right angles to the slope of the surface, while 
the land between is tilled. Why is this advantageous? 

11. Explain in detail why plowing up and down a hill-side is unwise. 

12. Other things being equal, would you expect crops to suffer more from 
protracted droughts on sandy or clayey soils? Why? 

13. In parts of China it is customary to plant alternate rows of leguminous 
plants (like peas and beans) and grains. How does this benefit the soil? 

14. Steel freight cars rapidly are replacing wooden ones, and re-enforced 
concrete (i.e. cement strengthened by steel) is being used for many new bridges 
in place of steel. Are these changes desirable from the standpoint of the conser- 
vation of natural resources? Reasons? 

15. Why are gold and silver, the "precious metals," much less essential to 
man than coal and iron? 



2 9 o ELEMENTS OF GEOGRAPHY 

References 

Chamberlin: Soil Wastage, in Proceedings of a Conference of Governors, 
Washington, D. C, May 13-15, 1908. (Government Printing Office, 1909.) 

Hopkins: Soil Fertility and Permanent Agriculture. (New York, 1910.) 

King: The Soil. (New York, 1902.) 

King: Farmers of Forty Centuries. (Madison, 19 11.) 

McGee: Soil Erosion; Bull. 71, U. S. Bureau of Soils. 

Merrill: The Principles of Rock Weathering, in Jour, of Geol., Vol. IV, 
pp. 704-724, 850-871. 

Merrill: Rocks, Rock Weathering, and Soils. (New York, 1897.) 

National Conservation Commission: Report of Commission; Sen. Doc. 676, 
60th Cong., 2nd Sess. (Contains several articles on mineral resources of the 
United States.) 

Ries: Economic Geology of the United States. 2d ed. (New York, 1910.) 

Shaler: The Economic Aspects of Soil Erosion, in Nat. Geog. Mag., Vol. VII, 
pp. 328-338, 368-377- 

Shaler: Man and the Earth. (New York, 1905.) 

United States Department of Agriculture: Washed Soils, Farmers' 
Bulletin 20. 

United States Geological Survey: Mineral Resources of the United 
States. (1910.) 

Van Hise: The Conservation of Natural Resources in the United States. (New 
York, 1910.) 

Warren: Elements of Agriculture. 3d ed. (New York, 1910.) 

Zon: The Future Use of Land in the United States; Circular 159, U. S. Forest 
Service. 



<• 



CHAPTER XIV 

CHANGES OF THE EARTH'S SURFACE DUE TO INTERNAL 

FORCES 

Slow Crustal Movements 

The crust of the earth seems to be firm and stable, except 'for 
occasional earthquakes and landslides, but it is in reality subject 
to very slow movements which, in the course of ages, produce great 
results. Such movements affect everything, from continents and 
ocean basins to minute particles of rock. Many of them result 
in warping the land and sea-bottom. Evidences of warping are 
so widespread that probably more of the earth's surface has been 
sinking or rising in recent geological times than has been standing 
still. Movements of land are seen most readily along coasts, 
because lands along the coast are compared easily with the level 
surface of the sea. 

Movement of coastal lands, (i) Old buildings and docks, 
near sea-level when built, are found submerged in some places and 
well above the sea in others. Clearly, this means a recent change, at 
these places, in the relations of land and sea. (2) Beds of sediment 
containing sea-shells, deposited beneath the sea in recent times, 
are found now above the water in north Greenland, on the Pacific 
coast of the United States, in the West Indies, on the west coast 
of South America, and in other places. On the slopes of Mount 
St. Elias, Alaska, modern sea-shells have been found attached to 
the rocks just as they once grew, but several thousand feet above 
sea-level. (3) Conversely, there are drowned forests along some 
coasts. Thus north of Liverpool, England, when the tide is out, 
numerous stumps may be seen standing on the beach (Fig. 157). 
Since trees of the kind represented by these stumps do not grow 
in salt-water, we conclude that the land where they grew has sunk 
below the level of high water. On the coasts of New Jersey and 
North Carolina, too, there are stumps having similar histories, 
several feet below sea-level. Many other facts prove that the 

291 



I 



292 



ELEMENTS OF GEOGRAPHY 



land and sea change their relations to each other, and that most 
coast-lines have been affected by such changes in recent times. 

The emergence of land may be due to (i) its rise, or (2) the sink- 
ing of the sea-level. Similarly, the submergence of land may be 
due to (1) its sinking, or (2) the rise of the sea. It is not possible to 
say, in all cases, whether it is the land or the sea-level which has 

changed; but it is cer- 
tain that the sea-level 
rises and falls from time 
to time, and that the land 
also moves. 

Causes of changes 
in sea-level. There are 
several things which may 
make the sea-level rise or 
fall. (1) The sinking of 
a portion of the ocean bed 
would lower the sea sur- 
face, while the elevation 
of a part of the sea floor 
would have an opposite 
effect. (2) Sediment 
washed from the land 
into the sea builds up the 
ocean floor, and so raises the surface of the sea. (3) Lavas poured out 
from volcanoes beneath the sea, and the deposits of corals and shell- 
bearing sea life, make the sea-level rise. (4) An increase or decrease 
in the total amount of land-water or ice would lower or raise the 
surface of the ocean. Since the oceans are all connected with one 
another, each of the above changes would affect the sea surface 
everywhere, and by the same amount. Other factors which will 
not be discussed here also affect the surface of the sea, and some of 
them make it higher in certain places than in others. 

Changes of level in the interiors of continents. Changes of 
level are perhaps as common in the interiors of continents as along 
coasts, but they are not detected so easily, since there is no level 
surface like the sea with which to make comparisons. There are 
raised beaches about many lakes, as about the Great Lakes and 
Great Salt Lake (Fig. 158); but raised beaches about a lake may 
result from the lowering of the lake, either by the cutting down 




Fig. 157. Stumps laid bare on the beach 
at low tide; Leasowe, Cheshire, England. (From 
photograph by Ward.) 



\ 



CHANGES OF THE EARTH'S SURFACE 



293 



of its outlet or by evaporation. They do not, therefore, prove a 
rise of the land. In many cases, however, the old shore-lines about 
lakes are not level, as they were when formed. Some parts of the 
old shore-line about former Lake Bonneville (the ancestor of Great 
Salt Lake) are 300 feet higher than other parts of the same line. 
An old shore-line about the east end of Lake Ontario is more than 




Fig. 158. Shore of former Lake Bonneville, Utah. 
U. S. Geol. Surv.) 



(From photograph by 



400 feet above the lake, while the same shore-line passes beneath 
the water at the west end of the lake. Such warped shore-lines 
are found about many lakes, and show that the surface about the 
lake basins has suffered movement since the shore-lines were formed. 
Other phenomena, some of them discussed later, also show move- 
ment of large interior areas. 

Ancient changes of level. Layers of rock, deposited long ago 
as sediment beneath the sea, are now found over great areas, far 
above sea-level. Most of the solid rock beneath the Mississippi 
Basin, for example, was laid down as sediment beneath the sea, as 
shown by the shells of the sea animals which it contains. In the 
Appalachian Mountains, rocks formed in the same way are found 
up to heights of several thousand feet; in the Rocky Mountains 



294 ELEMENTS OF GEOGRAPHY 

up to 19,000 feet and more; in the Andes up to 16,000 feet; and in 
the Himalayas to still greater heights. It is certain, therefore, 
that changes of level have been great, and that vast areas have been 
affected. Great changes in the areas and in the relations of land 
and sea have occurred repeatedly in the distant past. Great and 
repeated incursions of the sea upon the continents, alternating with 
great extensions of the continents at the expense of the sea, have 
been among the most important events in the history of the earth, 
for they have shifted the sites of erosion and sedimentation, have 
modified climates, and have changed the distribution and condi- 
tions of plant and animal life. It is probable that in the course of 
the earth's history the lowering of the sea-level, because of the sink- 
ing of the ocean basins, has been greater than the rise of the sea- 
level, because of sedimentation from the land. This is perhaps the 
reason why wind, water, and ice have not been able to destroy the 
continents, as is their constant aim. 

The past changes in the relations of oceans and continents 
perhaps have gone even further than indicated above. Geology 
gives us reason for thinking (1) that Europe has been connected 
with North America, by way of Iceland and Greenland; (2) that 
North America has been connected with Asia, by way of Alaska; 
(3) that the Mediterranean Sea once connected freely with the 
Indian Ocean to the southeast; (4) that a northerly arm of this 
extended sea, covering eastern Europe and western Asia, completely 
separated these continents; (5) that Great Britain was once a part 
of the continent of Europe; and even (6) that South America once 
was connected with other southern continents, perhaps by way of 
Antarctica. 

Future changes of level. Changes of level between land and 
sea are likely to continue indefinitely, for the processes which cause 
them will occur in the future, so far as can be seen now, just as they 
have for ages past. 

Earthquakes 

Frequency and importance. Tremblings or quakings of the 
earth's surface occur frequently in many countries. Most of them 
are not felt, and are detected only by means of a delicate instru- 
ment (the seismograph) made to record them. For many years 
an average of several earth tremors a day have been recorded in 
Japan, and it has been said that some part of the earth's surface 



CHANGES OF THE EARTH'S SURFACE 



295 



probaBly is shaking all the time. The changes made in the surface 
of the land by earthquakes are slight, and they are important 
chiefly because a few strong earthquakes have occasioned great 
loss of life and property. 




Fig. 159. Map showing in black the principal earthquake regions of the Old 
World. (Montessus de Ballore.) 



Distribution. Figs. 159 and 160 show the principal earthquake 
regions of the world. Most of them lie near the edges of the con- 
tinental platforms, though some (in Asia) are far inland. Most 
of them are mountainous areas, though some are lowlands. Earth- 
quakes are perhaps most common in volcanic regions, though not 
confined to them. Not all the earthquakes of such regions have 



296 



ELEMENTS OF GEOGRAPHY 



been caused by volcanoes, for many of them have not occurred at 
times of volcanic activity. Except along the west coast of South 
America, the southern continents appear to be relatively free from 
earthquakes. This may be because earthquakes in most parts of 




Fig. 160. Map showing in black the principal earthquake regions of the New 
World. (Montessus de Ballore.) 

these continents would be less likely to be recorded than elsewhere. 
Some of the areas most affected by earthquakes are settled densely. 

Causes of earthquakes. Earthquakes are caused in various 
ways. During movements of the earth's crust, great cracks or 
fissures sometimes are formed in the surface of the land (Fig. 161). 
The walls of fissures may be displaced, or faulted. Faulting has 



i 



CHANGES OF THE EARTH'S SURFACE 



297 



caused many great earthquakes, the slipping of one great body 
of rock past another producing vibrations, which "in some cases have 
spread far from the center of disturbance. An Alaskan earthquake 
in 1899 was caused by a sudden displacement of more than 40 
feet, and the San Francisco disaster in 1906 resulted from a hori- 
zontal movement of 5 to 20 or more feet, along a line many miles 
in length. Earthquakes accom- 
pany violent volcanic eruptions; 
and in these cases the explosions 
which cause the eruptions are 
doubtless the cause of the 
quaking. Great landslides and 
avalanches may cause slight 
earthquakes, and it is probable 
that slumping on the slopes of 
deltas and on the outer faces of 
the continental shelves produces 
similar results. Very slight 
shocks are perhaps caused in 
still other ways. 

It is probable that most 
earthquakes are incidents of the 
widespread movements to which 
the crust of the earth is sub- 
ject, movements which are due 




Fig. 161. Fissure in floor of Kilauea, 
Hawaii. 



primarily to the continued adjustment of the outside of the earth to 
a shrinking interior. In general, these movements are too slow to 
produce vibrations which we can feel; but they are sufficient, in rare 
cases, to produce great earthquakes. 

Destruction of life and property. Except along the plane of 
slipping, the actual movement of the land surface during an earth- 
quake is very slight; in most cases, but a small fraction of an inch. 
It is the suddenness of the shock which overthrows and destroys 
buildings and other objects on the surface. That a sudden but 
very slight movement of the ground may do this will be apparent 
when it is remembered that a quick, sharp tap on the side of a table 
may overthrow all loose objects upon it, even though the movement 
of the table itself is very slight. 

Earthquakes in thickly settled regions have in some cases caused 
an appalling loss of life and property. The most disastrous earth- 



298 



ELEMENTS OF GEOGRAPHY 



quake in North America occurred in and about San Francisco in 
April, 1906. A large part of the city was burned by the fire which 
followed the shock. More than 700 lives were lost, and between 
ioo ; ooo and 200,000 people were made homeless. Some 25,000 
buildings (Fig. 162) were destroyed in the earthquake and fire, having 
an estimated value of more than $100,000,000. The preceding year 
(1905) a great earthquake in India (Kangra) destroyed nearly 




Fig. 162. The new library building at Stanford University, after the earth- 
quake of April, 1906. (Moran.) 



19,000 lives and more than 112,000 buildings. About 100,000 
people were killed in the earthquakes in southern Italy in 1908. 
In the case of such earthquakes, the shattered nerves and reduced 
efficiency of thousands of people, not otherwise injured, represent 
an enormous additional loss. In some countries where earth- 
quakes are frequent, like Japan, much attention has been given 
to constructing buildings in such a way as to withstand the 
shocks. 

When an earthquake disturbs the sea-bottom, a series of waves 
is set in motion. These waves rush upon neighboring coasts, and 
in some cases (e. g., in Sicily in 1908) they have done great damage. 
Millions of marine animals and plants were killed in Yakutat Bay 
during the Alaskan earthquake of 1899. The greater frequency 
of earthquakes in Nicaragua was one factor in favor of selecting the 
Panama route for the Isthmian Canal. 



', 



CHANGES OF THE EARTH'S SURFACE 299 

VULCANISM 

Volcanoes 

A volcano is a vent in the earth's crust out of which hot rock 
comes (Fig. 163). The hot rock may flow out in liquid form (called 
lava), or it may be thrown out violently in solid pieces. It is gen- 
erally built up into a cone (Fig. 164), which may become a mound, a 
high hill, or even a high mountain. Quantities of gases and vapors 
are discharged along with the hot rock. 

There is a hollow, called the crater, in the top of most volcanic 
cones. Craters vary greatly in size, some of the larger ones being 
two or three miles across. While the volcano is active, an opening 
leads down from the crater to the source of the lava, at an un- 
known depth. 

Common phenomena of an eruption. In the explosive type 
of eruption, rumblings and earthquake shocks, due to explosions 
within the throat of the volcano, may occur for weeks or months 
previous to a violent outbreak. As the explosions become violent, 
dust, cinders,, and solid pieces are shot forth and fall upon the sides 
of the cone, while the summit of the mountain is shaken. The 
clouds of condensed steam and dust rising from the crater darken 
the sky, and torrents of rain, falling on the fine dust, may form 
rivers of hot mud. Liquid lava may or may not accompany the 
discharge of solid material. In the quiet type of eruption, the lava 
rises in the crater and occasionally overflows its rim; but more com- 
monly it breaks out through cracks in the side of the cone. 

There is little or no burning in a volcano, for there is little or 
nothing to burn. There is, therefore, no smoke. What appears 
as smoke is mostly cloud, blackened by volcanic dust. 

The products of volcanoes. Lava is a term applied both to 
the liquid rock which issues from a volcano, and to the solid rock 
which results from its cooling (Fig. 165). It takes on various forms 
as it becomes solid. If it hardens under little pressure, as at the 
surface, the gases and vapors which it contains may expand, and 
it may be converted into a sort of rock froth. Under other con- 
ditions it may form compact rock. 

Most of the solid materials blown out of a volcano are pieces 
of lava which solidified before they were shot out, or during their 
flight in the air. They include masses of rock tons in weight, and 
smaller pieces of all sizes down to minute particles of dust (commonly 



3°° 



ELEMENTS OF GEOGRAPHY 



called volcanic ash) . The dust in many cases is shot high into the 
air, and, being light, is scattered broadcast by the winds, some 




Fig. 163. Taal Volcano, Philippine Islands, in eruption. (Gilchrist.) 

of it coming to rest thousands of miles from its source. The liquid 
lava and the larger fragmental materials, on the other hand, stay 



< 



CHANGES OF THE EARTH'S SURFACE 



301 



near the vent. As already indicated (p. 259), all rocks formed by 
the consolidation of lavas are igneous rocks. 

The gases and vapors which issue from volcanoes are of many 
kinds. Some are poisonous, and some have temperatures so high 
as to be destructive to life, as in the case of Mont Pelee, in 1902. 

Most soils produced by the decay of volcanic materials are rich 
in the mineral elements of plant food, and are highly productive 
when well watered. 
The volcanic soils of 
the Spice Islands (Mo- 
luccas), Java, and other 
islands of the East In- 
dies, support a luxuri- 
ant vegetation. On the 
other hand, volcanic 
deposits weather slowly 
in a dry climate like 
that of Arizona, and 
support a scanty veg- 
etation. The San 
Francisco Mountains, 
volcanic mountains 
near Flagstaff, Arizona, 
are high enough to com- 
pel an increase of rainfall from the passing winds, and their slopes 
therefore support a splendid forest in the midst of the surrounding 
desert. These contrasts emphasize the fact that climate may be 
the controlling factor in the productivity of the soil. 

Number. The number of active volcanoes is not known defi- 
nitely, but is estimated at 300 to 400. Something like two-thirds 
of them are on islands, and the remainder on the continents. 

Distribution. The general distribution of active volcanoes is 
shown in Fig. 166. Many are arranged in belts, within which some 
are in lines. The most marked belt nearly encircles the Pacific 
Ocean. The volcanoes of the West Indies and of Java and 
Sumatra sometimes are considered as forming branches of the main 
belt. Outside this belt, volcanoes are numerous in and about the 
Mediterranean Sea, and there, are many others which cannot be 
connected with any well-marked system. 

Most volcanoes are in the sea or near it. Many are in moun- 




Fig. 164. Cone of Ngauruhoe, New Zealand. 
(Marshall.) 



302 



ELEMENTS OF GEOGRAPHY 



tain regions, though they do not occur in all mountains. Many of 
the active volcanoes lie near the line where the continental plateaus 
descend to the ocean basins. This is perhaps the most significant 
feature of their distribution. Many volcanoes are associated with 
lands which have been raised or lowered recently. 

Topographic effects of volcanoes. By making cones, vol- 
canoes become in certain places important factors in shaping the 




Fig. 165. Recent flow of lava from crater of Kilauea, Hawaii. (U. S. Forest 
Service.) 



surface of the lithosphere. Some volcanic cones make mountains 
of great size, like Mt. Rainier (Tacoma) in Washington, Mt. Hood 
in Oregon (Fig. 167), Mt. Shasta in California, Orizaba in Mexico, 
and others. All those named are so high that snow-fields and glaciers 
are found on their slopes. Volcanic cones are far more numerous 
than active volcanoes, for the cones of many extinct volcanoes 
still remain. 

Many small islands and some large ones are due chiefly or 
wholly to the building of volcanic cones on the ocean-bottom. The 
Aleutian Islands, the Hawaiian Islands, and many islands of Aus- 
tralasia were formed in this way. Iceland,. too, is largely volcanic. 
Many volcanic islands are bordered by sea cliffs, and are therefore 
nearly inaccessible. The craters of a few nearly submerged volcanic 



CHANGES OF THE EARTH'S SURFACE 



303 



cones form excellent harbors. Breaches in the crater walls have 
admitted the sea, and serve as gateways for ships. Lyttelton, an 
important port of New Zealand, has a harbor of this kind. 




Fig. 166. Map showing the distribution of volcanoes. (Russell.) 

Destruction of volcanic cones. Volcanic mountains, like all 
other elevations on the land, are subject to change and destruction. 
They may be de- 
stroyed partially by 
violent explosions. 
Again, the entire sum- 
mit of a volcanic 
mountain may sink, 
leaving a great de- 
pression, or cal.dera. 
Crater Lake, Oregon 
(Fig. 168), the deepest 
lake in North Amer- 
ica, occupies a caldera 
five or six miles in 
diameter, and 4,000 

feet deep. The lake is surrounded by nearly vertical walls 900 
2,200 feet high. Since the sinking of the top, a small cone, now 
island in the lake, has been built. 




Fig. 167. Mt. Hood, a snow-capped mountain. 



to 
an 



3°4 



ELEMENTS OF GEOGRAPHY 



Volcanic cones are destroyed also by the slow processes of weather- 
ing and erosion (p. 467). Wind and rain attack them as soon as they 
are formed, but the results are not conspicuous until the volcano is 
extinct and the cone stops growing. The many cones of extinct 
volcanoes in western United States are in various stages of destruc- 
tion. Some in j^rizona, California (Fig. 169), Idaho, and Oregon 




Fig. 168. Portion of Crater Lake, Oregon. (Copyright by Kiser Photo Co.) 



were formed so recently that they have suffered but little erosion. 
Fig. 170 shows a high mountain built by a former volcano. It 
still retains its conical form, but its steep upper slopes are furrowed 
by ravines and valleys, several of which contain glaciers. Fig. 171 
shows an old volcanic mountain which probably once rivaled 
Vesuvius, now worn into irregular hills. 

When a volcano ceases to be active, the passage from the inte- 
rior may be filled with hardened lava. This may be much more 
resistant than the rest of the cone, and after the latter is worn away, 
the plug, which becomes a hill as its surroundings are removed, 
may still mark the site of the former volcano. Some of these vol- 
canic necks, or plugs, are conspicuous. In central New Mexico a 



CHANGES OF THE EARTH'S SURFACE 



305 



number of them rise by precipitous slopes 800 to 1,500 feet above 
their surroundings. 

Destructiveness. Like earthquakes, some volcanoes have de- 
stroyed great numbers of lives and much property. During an erup- 
tion of Vesuvius in 79 
A. D., Pompeii, a city 
of about 20,000 in- 
habitants, was buried 
by cinders and ashes 
(Fig. 172), and Her- 
culaneum was over- 
whelmed by streams 
of hot mud. Some of 
the later eruptions of 
this volcano also have 
been very destructive. 

That of 163 1 was especially violent, destroying some 18,000 lives. 
One of the most violent and destructive volcanic eruptions of which 
there is record was that of 1883 in Krakatoa, an island in the Strait 
of Sunda, between Sumatra and Java. During a series of terrible 




Fig. 169. Typical cinder cone, Clayton Valley, 
California. 




Fig. 170. Mt. Shasta, a typical volcanic cone furrowed by erosion, but 
retaining its general form. (U. S. Geol. Surv.) ♦ 



explosions, about two-thirds of the island was blown away, and the 
sea is now nearly 1,000 feet deep where the center of the mountain 
formerly was (Figs. 173 and 174). Sea waves spread to Cape Horn, 
and possibly to the English Channel. On the shores of neighbor- 



3° 6 



ELEMENTS OF GEOGRAPHY 



ing islands the water rose 50 feet. More than 36,000 persons per- 
ished, mostly by drowning, and 295 villages were destroyed, wholly 
or partially. 

The volcano of Mont Pelee is on the island of Martinique, one 
of the Lesser Antilles, at the eastern border of the Caribbean Sea. 




Fig. 171. Marysville Buttes in contour. North-central California. (U. S. 
Geol. Surv.) 



Its cone descends by steep slopes to the sea on all sides but the 
south, where it is bordered by a plain on which the city of St. Pierre 
formerly stood. After slumbering for more than fifty years, the 
volcano became active in the spring of 1902. On May 8th a heavy 
black cloud, probably composed of steam, sulphurous vapors, and 
dust, and having an estimated temperature of 1,400° to 1,500° F., 



CHANGES OF THE EARTH'S SURFACE 



307 



swept down through a gash in the crater's rim, and out over the 
plain to the southwest. In two minutes it struck the city of St. 
Pierre, five miles distant, which was demolished at once (Fig. 175). 




Fig. 172. The ruins of Pompeii. (Doseff.) 

Buildings were thrown down, statues hurled from their pedestals, 
and trees torn up. Explosions were heard in the city as the cloud 
reached it, and flames burst out, started either by the heat of the 



Forsaken I 



Lang I. 





Fig. 173. Fig. 174. 

Fig. 173. Krakatoa Island and surroundings before the eruption of 1883. 

Fig. 174. Krakatoa Island and surroundings after the eruption of 1883. 
The numbers indicate the depth of the water in fathoms (a fathom = 6 feet) in 
both figures. 

gases, or the red-hot particles of rock which the gases carried. A 
few minutes later a deluge of rain, mud, and stones fell, continuing 
the destruction. With but two exceptions, the entire population, 



I 



3 o8 



ELEMENTS OF GEOGRAPHY 




increased to some 30,000 by refugees from the surrounding country, 
was wiped out of existence. The chief causes of death seem to 
have been (1) suffocation by the noxious vapors and gases, and 
(2) the great heat. Other causes of death were blows from stones 
thrown from the volcano, burns from hot rock, dust, and steam, 

and cremation in burning 
buildings. 

Volcanic eruptions in Ice- 
land in 1873 caused a con- 
siderable emigration from 
the island. 

Igneous Phenomena Not 

Strictly Volcanic 
Fissure eruptions. Lava 
sometimes rises to the sur- 
face through great fissures 
instead of through the rela- 
tively small vents of vol- 
canoes. From such fissures 
floods of lava may spread 
over the surrounding coun- 
try for hundreds of miles. (What determines the distance to which 
the lava flows?) Such lava floods once occurred in Oregon, Wash- 
ington, and Idaho, where by successive flows the former hills and 
valleys were buried, and a vast plateau 200,000 square miles or 
more in extent was built up (Fig. 176). In some places, the nearly 
level surface of the plateau meets the mountains along its border 
somewhat as the sea meets the land, while islands of older rock 
rise above it. 

In this lava plateau, the Snake River has excavated a great 
canyon 4,000 feet deep in some places, and 15 miles wide. The 
walls of the canyon show that in some cases successive beds of lava 
are separated by layers of soil in which the roots and trunks of trees 
are preserved. 

An older lava plateau of greater size, and more dissected by 
erosion, occurs in central and southern India. Still others, now 
made rough by erosion, are found on the north coast of Ireland 
and the west coast of Scotland, and some of the islands off Scot- 
land are remnants of an old lava plateau. 



Fig. 175. The ruins of St. Pierre, Mar- 
tinique. (Hovey.) 



CHANGES OF THE EARTH'S SURFACE 



309 




Lava flows of the North- 



While fissure eruptions of lava sometimes build up plateaus or 
raise the level of the plains on which they spread, they do not 
commonly give rise to moun- 
tains; but mountains may be 
developed from them, as they 
are dissected by stream erosion. 

Intrusions of lava. Most 
of the lava forced upward from 
great depths probably fails to 
reach the surface, and solidifies 
underground. Such rocks may 
be exposed at the surface 
through the wearing away of 
the rocks which overlay them. 
Indeed, much of the igneous 
rock at the surface is intrusive 
rock. Great masses of intruded 
lava may bulge up the overlying strata, making domes, some of 
which reach the size of mountains (Fig. 177). The Henry Moun- 
tains of Utah are examples. 
There are also deep-seated in- 
trusions of still greater size and 
in many cases of irregular form 
(called batholiths). As exposed 
by the removal of the rocks 
which once covered them, some 
batholiths occupy thousands of 
square miles. In places, lava 
has been forced in between 
beds of rock in sheets (forming 
sills), and into cracks (forming 
dikes; Fig. 178). 

Intrusions of lava may give 
rise to topographic features of 
importance after erosion has 
affected the regions where they 
occur, for the hardened lava 
(igneous rock) is in many cases 

harder than its surroundings. Many dikes form ridges. Intruded 
sheets of lava, if they have been tilted from a horizontal position, 




Fig. 177. Diagram of a laccolith. 




Fig. 178. Diagram of dikes and sills. 
What changes have occurred since the 
dike-rock was intruded? 



I 



3io 



ELEMENTS OF GEOGRAPHY 



may also form ridges, and these ridges may be so high as to be called 
mountains. The Palisade Ridge of the Hudson (Fig. 179), and most 
of the mountains of the Connecticut Valley, are examples. The 
steep ridges so important in the battle of Gettysburg are smaller 
examples of the same sort. Granite batholiths form the cores of 
many of the great mountain ranges. 

Causes of Vulcanism 
The causes of vulcanism lie outside the field of geography, and 
they are not well known. How the liquid rock is formed, the 
depth of its source, and how it makes its way toward the surface, 



l' : v 



Sms 



**■<*>. 







Fig. 179. The face of the Palisade Ridge, west of the lower Hudson River. 

are unsolved questions. The old notion that volcanic vents are 
connected with a liquid interior has been abandoned. 

It seems probable (1) that lava is being formed all the time, 
in spots, in the deep interior, and (2) that it is all the time finding 
its way toward the surface, but faster and in greater quantities at 
some times than at others. The regions where the crust is least 
stable, that is, where there is movement, are the regions most likely 
to afford the lava a place of escape. 



\ 



CHANGES OF THE EARTH'S SURFACE 



3ii 



Questions 

1. At the west end of the island of Crete, in the Mediterranean Sea, old docks, 
near sea-level when built, are found many feet above the water on dry land. At 
the east end of the island, ancient buildings are under water. Was the change 
in the relation of land and sea thus recorded due to movement of the sea surface, 
or of the land? Why could it not have been due to the other? 

2. How would the coast-line of North America be changed if the bottom 
of the Indian Ocean were to sink enough to lower the surface of that sea 200 feet? 

3. Other things being equal, are buildings situated on solid rock or on loose 
sediments more likely to be destroyed in the event of an earthquake? Why? 

4. Other things being equal, which are more enduring, volcanic cones built 
of lava- or of cinders? Why? 

5. Will soil form quickly or slowly on 
the recent (1902) volcanic deposits of Mar- 
tinique and St. Vincent? Why? 

6. To what extent may earthquakes 
and volcanic eruptions be predicted? 

7. (1) What was the origin of the 
mountain in the right hand foreground of 
Fig. 180? The evidence? (2) Has much 
or little time elapsed since its formation? 
How told? (3) What is the probable his- 
tory of the curving ridge at the left? 




Fig. 180. 



PP 



Bonney: 
Diller: 
237-268. 
Diller: 



(San Francisco, 1907.) 



(New York, 1899.) 



References 

Earthquakes 
Dutton: Earthquakes. (New York, 1904.) 
Hobbs: Earthquakes. (New York, 1907.) 
Jordan (Editor) : The California Earthquake of igo6. 

Volcanoes 
Volcanoes: Their Structure and Significance. 

Mt. Shasta, a Typical Volcano, in Physiography of the United States, 
(New York, 1895.) 

The Geology and Petrography of Crater Lake National Park, Prof. 
Paper No. 3, U. S. Geol. Surv. 

Dutton: Hawaiian Volcanoes, in 4th Ann. Rept., U. S. Geol. Surv., pp. 
81-219. 

Gilbert: Geology of the Henry Mountains, pp. 18-60; U. S. Geog. and Geol. 
Surv., Rocky Mt. Region. (Washington, 1877.) 

Heilprin: Mont Pelee and the Tragedy of Martinique. (Philadelphia, 1903.) 
Hill: Report on the Volcanic Disturbance in the West Indies, in Nat. Geog. 
Mag., Vol. XIII, pp. 223-267. 

Hovey: The Eruption of La Soufrierc, St. Vincent, in May, 1902, in Nat. 
Geog. Mag., Vol. XIII, pp. 444-459. 

Jaggar: The Eruption of Mount Vesuvius, April 7-S, 1906, in Nat. Geog. 
Mag., Vol. XVII, pp. 318-324- 



3 i2 ELEMENTS OF GEOGRAPHY 

Judd: Volcanoes. (New York, 1893.) 
Russell: Volcanoes of North America. (New York, 1897.) 
Russell: The Recent Volcanic Eruptions in the West Indies, in Nat. Geog. 
Mag., Vol. XIII, pp. 267-285. 

Russell: Volcanic Eruptions on Martinique and St. Vincent, in Nat. Geog. 
Mag., Vol. XIII, pp. 415-436. 

The topics of this chapter are discussed at greater length in the larger text- 
books of Geology and Physiography, under Changes of Level, Secular Changes of 
Level, Crustal Movements, Earthquakes, Volcanoes, etc. Among the better books 
for use in connection with these and kindred topics are: 

Chamberlin and Salisbury: College Geology. (New York, 1909.) 
Chamberlin and Salisbury: Geologic Processes and Their Results, Vol, I. 
(New York, 1905.) 

Chamberlin and Salisbury: Earth History, Vols. II and III. (New York, 
1906.) 

Dana: Manual of Geology. (New York, 1894.) 
Geikie: Text-book of Geology. (New York, 1903.) 
Salisbury: Physiography, Advanced Course. (New York, 1909.) 
Scott: An Introduction to Geology. 2d. ed. (New York, 1907.) 



i 



CHAPTER XV 

MODIFICATION OF LAND SURFACES BY EXTERNAL AGENTS 

The surface of the land is being changed all the time by various 
agents, especially by wind, by water in the ground, by running water, 
by ice, and in minor ways by diverse forms of life. 

The Work of the Wind 

Winds modify land surfaces by removing dust and sand from 
certain places, and depositing them in others. Wind-driven dust 
and sand may wear exposed surfaces of rock. 

Transportation. Transportation of fine materials by the wind 
is important where dust or dry sand is exposed to strong winds, as 
in semi-arid regions, and in deserts, which comprise about one-fifth of 
the land (11,500,000 square miles). Desert winds often sweep up 
"clouds" of dust which may be seen for miles, and a single storm 
may move millions of tons of dust and sand. The dreaded simoon 
of the Sahara has been known to destroy entire caravans, death 
resulting from suffocation in the dust-laden air. While trans- 
portation by the wind is most important in arid regions, it is by 
no means confined to them. Even in regions which are not arid, 
much of the dust in the air consists of fine particles of earthy 
matter blown up from streets, plowed fields, and surfaces not well 
covered with vegetation. 

Particles of dust are much heavier than air, and gravity tends 
to bring them down. Yet they may remain in the air for a long 
time (1) because they are so small that they do not fall readily, 
and (2) because there are many upward currents in the air which 
carry the particles up in spite of gravity. As a matter of fact, the 
dust of the atmosphere always is settling, and the supply is being 
renewed constantly. Not only may dust remain in the air for a 
long time, but it may be carried great distances. A severe storm 
in March, 1901, carried dust northward from the Sahara, and 

313 



3i4 



ELEMENTS OF GEOGRAPHY 



deposited it in diminishing amount over Europe as far as southern 
Denmark. In 1883, volcanic dust from Krakatoa (p. 306) was car- 
ried around the earth by the upper winds in about two weeks, its 
progress being indicated by the brilliant sunsets to which it gave rise. 
Abrasion. Sand blown against a rock has the effect of a sand- 
blast, and wears the rock away. If some parts of the rock surface 
are harder than others, the less hard parts are worn more rapidly. 

Where abundant sand is driven 
by the wind, projecting rocks 
may be carved into fantastic 
forms (Fig. 181). Abrasion by 
wind-driven sand is of little con- 
sequence in a plain country 
where the climate is moist, and 
where the rock is covered with 
soil; but it is of much conse- 
quence in arid and semi-arid 
regions where the topography 
is rough, and where hills and 
points of bare rock are numer- 
ous (Fig. 182). In deserts and 
along sea coasts, telegraph poles 
have been cut off near the 
ground by wind-blown sand. In 
some such places, stones are 
piled about the bases of the poles, so that the stones, rather than 
the poles, get the sand blast (Fig. 183). Windows have been made 
opaque in a few hours by the wear of sand blown against them. 

Wind deposits. Wind deposits of sand and loess (Fig. 184) 
have been described in connection with soils (p. 265). Sand usually 
is carried along within a few feet of the ground, and is therefore 
likely to lodge about any obstacle which blocks its way. Eleva- 
tions of wind-deposited sand are dunes. They vary greatly in form, 
some being long, narrow ridges, and others irregular mounds, and 
they range in height from a few feet to more than 400 feet. Small 
dunes are much more common than large ones. Dunes are found 
mostly near the sources of abundant dry sand. They are com- 
mon, along much of the Atlantic coast of the United States, where 
sand is washed up on the beach by waves. After drying, it 
becomes the prey of the wind. Winds from the west blow this sand 




Fig. 181. Rocks carved by the wind. 
(Bastin.) What inferences may be made 
concerning the character of the rocks? 



MODIFICATION OF LAND SURFACES 



3i5 



into the sea; those from other directions, but especially from the 
east, drift it up on the land. Where westerly winds prevail, as 




Fig. 182. Sandstone cliffs near Moab, Utah. (Cross, U. S. Geol. Surv.) 
What may be inferred concerning the climate of this region? The evidence? 



in most of the United States, most of the dunes along valleys are 
on their east sides. Dunes abound over thousands of square miles 
in the semi-arid parts of the Great Plains, 
as in western Nebraska, western Kansas, and 
some parts of Wyoming. They reach their 
greatest development in still drier regions, 
such as the Sahara. In some places, dunes 
are the most conspicuous feature of the land- 
scape. 

Sand is blown from the windward side 
of a dune and dropped on the leeward side, 
much of the time. This continued shifting 
of sand to the leeward side results in a slow 
migration of the dune. Farm lands, espe- 
cially near sea coasts, have been covered in F; g . js 3 . Telegraph 
this way, and forests have been buried (Fig. pole in southern Califor- 
i8 S ). Sometimes sand buries buildings (Fig. %£*£* &3* 
186), and in some places it causes much hall, U. S. Geol. Surv.) 




r 



3i6 



ELEMENTS OF GEOGRAPHY 



trouble along railways (Fig. 187). So disastrous is the migration of 
dunes along some coasts that measures are taken to prevent it. If 
a dune is covered with vegetation, its position is not likely to change 
so long as the plants remain, for they hold down the sand. Trees, 
shrubs, and grasses which will grow in sand sometimes are planted 
on dunes as soon as the latter are formed, to prevent further drifting 




Fig. 184. Deposit of loess near Vicksburg, Mississippi. The cut followed by 
the road has been developed by the wear of traffic and wind. (McGee, U. S. 
Bureau of Soils.) 



(Fig. 188). This has been done at various points on the western 
coast of Europe, where land is valuable, and to some extent in our 
own country, as at San Francisco, where the westerly winds drift sand 
in from the shore. Fig. 189 shows the effect of a clump of trees in 
holding sand. All the dune except the part held by the roots of the 
trees has been blown away. 

The amount of wind-blown sand not heaped up in distinct ele- 
vations probably far exceeds that in dunes. 

Summary. The more important phases of the work Of the 
atmosphere may be summarized here. (1) Of most importance is 
its work as an agent of weathering (pp. 261-262). (a) Through its 



MODIFICATION OF LAND SURFACES 317 




Fig. 185. Dunes advancing on a forest. Little Point Sable, Michigan. 




Fig. 186. The last house in Riggs, Oregon, a village overwhelmed by sand 
dunes. (Gilbert, U. S. Geol. Surv.) 



3i8 



ELEMENTS OF GEOGRAPHY 



effect on changes in temperature it influences the wedge work of 
ice, and the breaking of rocks by their expansion and contraction. 




Fig. 187. Sand drifted over a railway, Rowena, Washington. One rail 
shows at the left-hand side. (U. S. Dept. of Agri.) 



(b) The oxygen, carbon dioxide, and water vapor of the air unite 
chemically with various rock materials, and, by so doing, contrib- 




Fig. 188. Sand dune reclamation, Manistee County, Michigan. (Sketch 
from photograph by Forest Service.) 

ute to their decay. These processes prepare materials for removal 
by various transporting agencies. (2) The wind transports and 



MODIFICATION OF LAND SURFACES 



3i9 



deposits large amounts of fine material. Although most extensive 
in arid regions, this work has affected all land surfaces. Since the 
wind deposits much dust and sand in the sea, the aggregate effect is 
to lower the lands and build up 
the ocean-bottoms. (3) Rocks 
are abraded by wind-driven 
sand. This is most important 
in deserts, where the atmos- 
phere is, in many places, the 
chief agent of land reduction. 
(4) By controlling the condi- 
tions of evaporation and precip- 
itation, the atmosphere makes 
possible the work of streams and 
of glaciers, and the existence of 
land life. 

QUESTIONS 
1. Why are there many large 
dunes on the eastern side of Lake 
Michigan, and only a few small ones 
on the western shore? 




Fig. 189. The remnant of a dune 
held by roots. The surrounding sand not 
so held has been blown away. Head of 
Lake Michigan. 



2. Describe the sequence of events recorded by Fig. 199. 




Fig. 190. View on Little Point Sable, Michigan. 



320 



ELEMENTS OF GEOGRAPHY 



3. In many dune areas there are numerous depressions among the sand 
hills. In what ways may such depressions originate? 

4. Why are dunes formed along some river valleys and not along others? 

5. (1) What inferences may be made from Fig. 191 concerning (a) the charac- 
ter of the rocks, and (b) the climate? (2) What evidences of wind work are there 
in this picture? 




Fig. 191. View in Red Mountain, Arizona. (Atwood.) 



REFERENCES 

Bonney: The Work of the Atmosphere, in The Story of Our Planet, pp. 91- 
102. (London, 1893.) 

Cobb: Where the Wind Does the Work, in Nat. Geog. Mag., Vol. XVII, pp. 

310-317- 

Davis: The Geographical Cycle in an Arid Climate, in Jour, of Geol., Vol. 
XIII, pp. 381-407. 

Geikie, J.: Earth Sculpture, pp. 250-265. (New York, 1898.) 

Hitchcock: Controlling Sand Dunes in the United States and Europe, in Nat. 
Geog. Mag., Vol. XV, pp. 43-47. 

Kearney: The Country of the Ant Men, in Nat. Geog. Mag., Vol. XXII, 
PP- 367-382. 

Udden: Erosion, Transportation, and Sedimentation Performed by the Atmos- 
phere, in Jour, of Geol., Vol. II, pp. 318-331, and Pop. Sci. Mo., Vol. XLIX, 
pp. 655-664. 

See also general texts mentioned on p. 312. 



MODIFICATION OF LAND SURFACES 321 

Ground- Water 
general considerations 
The fate of rain-water. The average annual rainfall of the 
United States is about thirty inches. This means that a total of 
about 1,500 cubic miles of water (enough to cover New England to 
a depth of about 1,000 feet) fall as rain or snow in this country 
each year. It is estimated that about one-half of this water evap- 
orates, that about one-third of it runs off over the surface, and that 
the remaining one-sixth is consumed by plants or sinks beneath 
the surface. The relative amounts disposed of in these different 
ways vary greatly from place to place, and from time to time. The 
proportion of the rainfall which sinks beneath the surface is deter- 
mined chiefly by (1) the slope of the ground, (2) the porosity of 
the soil and bed rocks, (3) the nature of the rainfall (whether, for 
example, the water falls in a gentle drizzle or a driving downpour), 

(4) the character and amount of vegetation on the surface, and 

(5) the amount of water already in the ground. (What condition, 
under each of the above headings, would cause most water to sink 
under ground? Reasons.) 

The ground-water surface. It is possible almost anywhere 
to dig wells deep enough so that they will have a constant supply 
of water. This means that the surrounding rocks are full of water 
below the level of the water in the wells. The surface below which 
the subsoil and rocks are full of water in any given region is the 
water surface or water table for that region. In swamps and marshes 
the water table is at or near the surface of the ground, while in arid 
regions it may be hundreds of feet below. In humid regions it 
is seldom more than 50 or 60 feet below the surface. The position 
of the water table also varies from time to time. It is higher after 
heavy rains, and lower during and after long droughts. 

Amount of water underground. The pores and openings in 
the rocks below the water surface are full of water. Some porous 
rocks contain 30 per cent or more of their volume of water; very 
compact rocks may be able to hold only a fraction of 1 per cent. 
A porosity of 10 per cent means about 1 gallon of water per cubic 
foot. In general, rocks near the surface have more and larger pores 
and cracks than those at greater depths. Pores and cracks become 
very small at the depth of a few thousand feet, and probably none 
exist below a depth of five or six miles, because the rock pressure 



322 



ELEMENTS OF GEOGRAPHY 



is so great. If this is true, water does not descend to greater depths. 
There is water enough underground to form a layer at the surface 
having a depth variously estimated from 96 feet to more than 1,000 
feet. It is probably not less than the mean of these two figures, 
and perhaps nearer the larger than the smaller. (What would 
need to be known in order to determine the amount accurately?) 
Circulation of ground- water. Ground- water is moving con- 
stantly. This is shown, for example, by the constant flow of springs 




Fig. 192. Diagram showing the relation of the level of ground-water (the 
broken line) to the surface of the ground and to a lake and river. 



and by the fact that after a well is pumped "dry," it soon fills again 
to the former level, because water seeps in from the surrounding rocks. 

The reasons why ground-water moves may be understood readily. 
Rain does not fall equally everywhere. If there is a heavy shower 
in one part of a flat region where the ground-water surface is level, 
the soil and rock where the rain falls may become filled with water, 
and, as a result, the ground-water surface there is raised temporarily. 
Under these conditions, ground-water will flow from the place where 
the water surface is higher to places where it is lower. In the 
subsoil or bed rock, the water spreads more slowly than it would 
nearer the surface, because it does not move readily through the 
small pores and cracks. 

The ground-water surface is not always level, even in a region 
where the rainfall is uniform. Other things being equal, it is higher 
beneath high iand, and lower beneath low land (Fig. 192), and in 
this case, the water under the higher land moves out to lower lands. 
The tendency is for the water surface below the high land to sink 
until it is as low as that beneath the low land; but in moist climates 



MODIFICATION OF LAND SURFACES 



323 



it rains so often that the water surface under the hills almost never 
sinks to the level of the water in the surrounding low lands, before 
it is raised again by rains. 

Water which sinks to great depths commonly follows a devious 
course before again reaching the surface. At first its movement is 
chiefly downward, and is relatively rapid because of the many large 




Fig- i93- 
in the rocks. 



View in quarry, Sturt Valley, South Australia, showing openings 
(Greenlees.) 



cracks and pores in the ro'cks near the surface (Fig. 193). Farther 
down, its movement is largely sideways (Why?). In places it may 
be forced (by what?) toward the surface. It may flow slowly for 
many miles along a crooked course, through small openings, before 
it reaches a passageway leading to the surface. Through such 
an opening it may issue with great force as a spring or flowing well. 
Fig. 194 suggests the intricate circulation of the water which issues 
in a deep-seated spring. Some water flows underground to the 
sea or to lakes, and issues as springs beneath them. Much ground- 
water, too, seeps out in such small quantities that it does not appear 
to flow, and does not make a spring. 



3 2 4 



ELEMENTS OF GEOGRAPHY 




Ground-water moves in still other ways. Much of it is taken 
up by roots, passes up through the plants, and comes out through 
their leaves (is transpired) into the air. The amount of ground- 
water returned to the air through plants depends largely on (i) the 
density and character of the vegetation, (2) the temperature, (3) 
the relative humidity, (4) the velocity of the wind, and (5) the length 
of the growing season. (Compare the amount disposed of in this 
way in western Washington and Arizona; western Kansas and 

southern Florida.) It has been 
estimated that the amount of 
water returned to the air daily 
by forests through their foliage 
varies under different condi- 
tions from 1,000 to 20,000 or 
more pounds per acre, during 
the growing season. About 
5,000 pounds of water are trans- 
pired by the foliage of corn-plants 
in the production of a bushel of 
corn. Again, water is evaporat- 
ing from the ground most of the 
time, even in regions where the 
soil appears to be very dry. It is probable that nearly all the water 
which sinks beneath the surface comes up again sooner or later, in 
some of these ways; but a little unites with solid mineral matter, as 
in iron rust (p. 261). 

The rate at which ground- water moves depends chiefly on (1) 
the porosity of the rock or soil, and (2) the pressure of the water. 
The rate at which water seeps through soils from irrigating ditches 
in the West is in most cases from one to eight feet per day; but in 
very porous soils it is sometimes as much as 50 feet per day. In 
a widespread formation of sandstone which underlies southern Wis- 
consin and northern Illinois, the rate of movement of ground-water 
has been estimated at half a mile a year. At this rate, rain-water 
which enters this formation 100 miles from Chicago would reach 
that city in about 200 years. 

Knowledge of the circulation of the upper part of the ground- 
water is important to every family using well-water for domestic 
purposes. Polluted well-water is very common on farms which 
might have pure and wholesome water. Great numbers of wells 



Fig. 194. Diagram showing the in- 
tricate underground drainage which issues 
in a deep-seated spring. (Geikie.) 



MODIFICATION OF LAND SURFACES 



325 



are so situated that ground-water moves toward them from cess- 
pools and stables. Largely as a result of this, typhoid fever is 
more common in many farming regions than in most cities. 

Uses and functions of ground-water. Ground-water is of vital 
importance in the economy of the earth and in human affairs. (1) 
It is important to plants. It dissolves the mineral elements of plant 
food and carries them to the 
roots. The amount of water 
available for plants is the most 
important factor conditioning 
their life in many regions. (2) 
Underground water supplies all 
springs and wells, the sources 
from which perhaps three- 
fourths of the people of the 
United States obtain their 
water for domestic use. (What 
are the other possible sources of 
supply?) 

The distribution of population in 
eastern United States was influenced 
greatly by running water and natural 
springs, until modern methods of well- 
digging were developed. Absence of 
springs, and dependence for two years 
upon the brackish water of the James 
River, were one cause of the high 
death-rate in the Jamestown colony. 

A supply of wholesome water helped to determine the location of the Pilgrim 
colony at Plymouth, and of the Puritan settlement at Boston. Many of the 
stockaded villages of the early western frontier were so located as to command a 
supply of water in the event of an Indian siege. The settlement of certain inter- 
stream areas in southern Wisconsin and in Illinois was delayed for years, partly 
because of the difficulty and expense of digging wells. In the arid West, springs 
and watering places determine the location of many villages and farms, and 
influence the course of trails and roads (Fig. 195). Their location is indicated 
on many maps for the benefit of travelers. 

Because of the intimate relation of ground-water to plant, ani- 
mal, and human life, it is highly important that the water table 
be kept near the surface of the ground. It is estimated that in 
eastern United States it has been lowered from 10 to 40 feet over 
large areas by cutting off forests and by careless methods of tillage 




Fig. 195. Map showing springs (by 
circles) and roads in the region of Flag- 
staff, Arizona. (From San Francisco 
Mountain Sheet, U. S. Geol. Surv.) 



326 ELEMENTS OF GEOGRAPHY 

which have increased the proportion of the rain-water which runs 
off over the surface. Indeed, it is estimated that at least three- 
fourths of the shallow wells and springs have failed in this part 
of the country. (3) Ground-waters bring about important changes 
in the character of the rocks through which they pass. These 
changes take place slowly, but they are going on all the time. 

The different kinds of springs and the work of ground-water 
may be discussed in greater detail. 

OUTFLOWING WATERS 

Hillside and fissure springs. Fig. 196 illustrates two kinds 
of springs. In the one, water descends through a more or less porous 
bed of rock, c, to a layer, a, which is compact. Much of the water, 
flows along this layer until the latter comes to the surface (out- 




Fig. 196. Diagram to illustrate two types of springs, as explained in text. 

crops), and there the water issues as a hillside spring, s. The great 
majority of springs are of this class, and most of them are small. 
In the other case (Fig. 196), the water moves through the porous 
layer, b, under pressure, until it reaches a crack which leads up to 
the surface. If the crack is open enough to afford a passageway, 
the water will follow it up to the surface, as at s' , forming a fissure 
spring. In such a situation there will be a spring only when the 
opening is lower than the water surface in the layer of rock which 
carries the water. This sort of spring is similar to a flowing well 
in principle, though in the latter case the opening is made by man. 

Artesian wells. Formerly, artesian wells were regarded as the 
same as flowing wells. Now, the name "artesian" often is applied 
to deep, ' drilled wells, whether they flow or not. Fig. 197 illus- 
trates the conditions necessary for flowing wells. They are: (1) 
A porous layer or bed of rock, A , underlying one which is not porous, 
and which prevents the water from escaping upward until it is pene- 
trated by the well hole, W. The porous bed must come to the 
surface in a region which is somewhat higher than the site of the 
well; and (2) enough rainfall where the porous bed comes to the sur- 



MODIFICATION OF LAND SURFACES 



327 



face to keep that bed well filled with water. Under these condi- 
tions, the water will gush up (Fig. 198), if a hole is made down to it. 




Fig. 197. Diagram illustrating the conditions necessary for flowing wells. 



Flowing wells may be but a few feet deep, or they may be thou- 
sands of feet deep. Thus there is one in St. Louis nearly 4,000 
feet deep, and many in New Jersey less 
than 100 feet in depth. Many villages 
and small cities get their water from 
artesian wells; but great cities, such as 
New York and Chicago, could not get 
enough in this way. Brooklyn obtains 
a part of its supply in this way, its 
artesian wells having a capacity of about 
22,000,000 gallons per day. In parts of 
the West, artesian waters are used exten- 
sively for irrigation, as well as for domes- 
tic and other purposes. The Black Hills 
of southwestern South Dakota receive 
much more rain than the surrounding 
plains (hence the dark forests which sug- 
gested their name). Porous sandstone 
beds coming to the surface about their 
flanks carry a part of this rain-water 
eastward for many miles beneath the plains. East of the upper 
Missouri River more than 1,000 artesian wells tap these sandstones, 




Fig. 198. An artesian well at 
Lynch, Nebraska. Flows more 
than 3,000 gallons per minute. 
(Darton, U. S. Geol. Surv.) 



328 



ELEMENTS OF GEOGRAPHY 



and obtain large quantities of water. In the Dakotas and probably 
in other artesian areas more wells have been drilled than are needed, 
and when not in use (in many cases this is the greater part of the 
time) the water from the flowing wells has been allowed to run off 
freely. This has reduced so greatly the pressure and the amount 
of water available, that villages and cities, formerly abundantly sup- 
plied from artesian wells, have been compelled to seek other sources 

of supply. In some of 
mmmi 



the arid states where 
the water problem is 
critical, as in Califor- 
nia, strict laws exist to 
prevent the waste of 
artesian and other un- 
derground waters (Fig. 
199). The San Ber- 
nardino artesian basin 
of southern California 
covers less than 175 
square miles, but is of 
great importance to the 
orange orchards. Here 
artesian and other 
waters are used with 
great skill. It is esti- 
mated, for example, that water in passing from the upper Santa Ana 
River (the chief stream of the district) to the sea is utilized for 
different purposes at least eight times. 

Geysers. Geysers are hot springs which erupt from time to 
time (Figs. 200 and 201). So far as known, they occur only in a 
few regions of recent volcanic activity, Yellowstone National Park, 
New Zealand, and Iceland. From a few geysers water is ejected to a 
height of 200 feet or more, by steam produced at some point in the 
geyser tube below the top of the water. It is believed that hot 
volcanic rocks make the water boil, and the expansion of the steam 
formed causes the eruptions. (How will the cooling of the rocks affect 
the frequency of eruptions? What will be the ultimate fate of exist- 
ing geysers?) Although interesting, geysers are of little importance. 
Other hot springs. ' Some springs are warm, and a few are hot. 
Where spring-water is hot, it is in some cases because it has been 




Fig. 199. An artesian well in southern Cali- 
fornia, showing method of shutting off the water 
when not in use. 



MODIFICATION OF LAND SURFACES 



3 2 9 



in contact with lava which came up from greater depths so recently 
that it has not yet become cold. In other cases the heat may be 
due to chemical changes taking place beneath the surface. There 

are more than 3,000 hot springs in the 
Yellowstone National Park, and many 
others in different parts of the country. 
Mineral and medicinal springs. All 
spring-water has some mineral matter in 
solution; but a spring is not commonly 





Fig. 200. Fig. 201. 

Fig. 200. The Wairoa Geyser, New Zealand. Shoots 1,500 feet. (New 
Zealand Gov't Tourist Dept.) 

Fig. 201. Waimancu Geyser, New Zealand. (Muir and Moodie.) 



called a mineral spring unless it contains (1) much mineral matter, 
(2) mineral matter which is unusual in spring-water, or (3) mineral 
matter which is conspicuous either because of its color, odor, or taste. 
Many mineral springs are thought— and some rightly— to have heal- 
ing properties, and so are known as medicinal springs. Many of the 



33 o ELEMENTS OF GEOGRAPHY 

famous watering-places and resorts for invalids are at hot mineral 
springs. The Hot Springs of Arkansas, Virginia, South Dakota, 
and Carlsbad (Bohemia) are examples. Many springs which are 
charged with gases are called mineral and medicinal, even though 
their waters are worthless for healing purposes. In 1910 mineral 
water was sold from about 700 springs in the United States. The 
amount of water sold was more than 62,000,000 gallons, valued at 
about $6,300,000. 

WORK OF GROUND-WATER 

Solution. All water which comes out of the ground has in 
solution some mineral matter dissolved, from the rock through which 
the water has passed. Pure water does not dissolve mineral mat- 
ter readily; but rain-water is not pure, for it dissolves gases from 
the air, and in sinking through the soil takes up the products of 
plant decay. With these impurities in solution, ground- water dis- 
solves most sorts of mineral matter more readily than pure water 
would. The amount of mineral matter brought to the surface 
through springs is very great. Thus the springs of Leuk (Switzer- 
land) have been estimated to bring to the surface more than 2,000 
tons of gypsum in solution yearly. By removing their soluble con- 
stituents, ground-water helps to make rocks crumble, and so to 
form soils (p. 261). 

Much of the ground-water finds its way to rivers after it seeps 
out. The larger part of the mineral matter in solution in rivers 
has come from ground-water which has flowed to them. Ail the 
rivers of the earth are estimated to carry nearly five billion tons of 
mineral matter to the sea in solution each year. The transfer of 
so much mineral matter in solution from land to sea, lowers the 
land. 

Some of the mineral matter carried to the sea in this way remains 
in the sea-water. Thus, most of the salt which has been carried to 
the sea remains there, probably, to this day. On the other hand, 
much of the mineral matter taken to the sea is used by sea animals 
(and some plants) for making their shells, tests, and bones, and 
these are left on the sea-bottom when the organisms die. 

Caverns and cavern life. By the dissolving work of ground- 
water, rock is made porous. Small pores and cavities are more 
numerous than large ones, but some of the openings produced in 
this way, such as Mammoth Cave in Kentucky, and Wyandotte 
Cave in southern Indiana, are very large- Such caves occur chiefly 



MODIFICATION OF LAND SURFACES 



33i 




in limestone, for this- is the most soluble of the common rocks. An 
underground cave is not, as a rule, one great chamber, but is made 
up of many chambers connected by smaller passageways (Fig. 202). 

Caverns do not furnish the conditions favorable for most sorts 
of life, for most plants and animals need light; yet there are several 
varieties of cavern animals, some living in the water and some in 
the damp air. These animals are so like those living above ground 
in the same region, that they are thought to be the descendants 
of animals which got into the caves 
from the surface. 

Cave animals show some pecu- 
liar features. They are colored less 
brightly than their relatives above 
ground. This is probably because 
of the absence of sunlight, which 
seems to have much to do with pro- 
ducing color in animals. Some cave 
animals have good eyes, some have 
imperfect eyes, and some have none. 
From these and other facts, we infer 
that the eyes of animals in dark 
caves tend to disappear. A third 

peculiar feature of cavern animals is the good development of their 
organs of touch. In the darkness the sense of touch is much more 
useful than sight. 

In Europe, certain caverns were the homes of primitive man, 
as shown by the human bones and the tools of various sorts which 
are found in them. Here, too, are found the bones of large animals 
which were killed for food or fur, and taken to the caves. On some 
of the bones of such animals, and on pieces of slate or wood, there 
are drawings, some of which are of animals no longer living in the 
region where the caves are. From this we infer that the people 
who lived in the caves dwelt there a long time ago. 

Deposition. After dissolving mineral matter, ground-water 
sometimes leaves a part of it in the pores and cracks of the rocks 
through which it flows. When cracks in the rocks are filled or 
partly filled by mineral matter deposited from solution, the fillings 
become veins (Fig. 203). Many ores of gold, silver, lead, zinc, copper, 
and other metals, occur in veins. Originally, most of the metals 
were scattered widely through the rocks, usually in the form of corn- 



Fig. 202. Vertical section of a 
cave in France. (After Robin.) 



332 



ELEMENTS OF GEOGRAPHY 



pounds. They first were dissolved, and then deposited by ground- 
waters in the cracks and openings where they are now found. Thus 
the work of ground-water has made the great deposits of most ores, 
so important to mankind (pp. 284-287). Ground-waters also deposit 
mineral matter among particles of loose sediment, cementing them 
into firm rock. 

Mineral matter brought to the surface by ground-water may 
be deposited there, as the result of various causes. (1) When water 

evaporates, the min- 
eral matter dissolved 
in it is left behind. 
This is one reason why 
kettles in which water 
is boiled become 
coated with mineral 
matter. (2) Certain 
gases dissolved in 
water help it to dis- 
solve mineral matter. 
If water contains 
much gas, which later 
escapes, as it is likely 
to when the water is 
heated or when it 
comes to the surface, 
some of the mineral 
matter in solution 
may be deposited. (3) 
Warm spring-water 
may give up what it 
holds in solution when it cools. (4) Microscopic plants grow in the 
waters which issue from some hot springs, as in Yellowstone Park, 
and by some process not well understood, extract mineral matter 
from the water, and cause it to be deposited. 1 

Solution and deposition may be going on at the same time, and 
even in the same place. Thus the original material of a buried shell 
may be dissolved and carried away at the same time that other 
material is left in its place, preserving the form of the shell. In the 
same way, wood may be replaced by mineral matter, giving rise 
to petrified wood, or wood "turned to stone." Such changes prob- 




Fig. 203. A quartz vein (the white band) in 
metamorphic rock. Muchals Caves, Kincardineshire, 
Scotland. 



MODIFICATION OF LAND SURFACES 



333 



ably take place slowly, the mineral matter which was in solution 
in the water replacing the woody matter as it decays. 

Mechanical work. Abrasion by ground-water is slight, since 
ground-water rarely flows in strong streams. Indirectly, ground- 
water helps to bring about changes of another sort. When the soil 
on a steep slope becomes full of water, its weight is increased greatly, 
and the water in it makes it move more easily. Under these cir- 
cumstances, it sometimes slides down. Such movements are known 
as slumping or sliding. 
If the slide is large, 
it usually is called a 
landslide (Fig. 204) . 
Slumping is very com- 
mon on the slopes of 
hills composed of clay 
or other loose matter. 
Many landslides have 
been very destructive. 
In 1903 there was a 
slide on Turtle Moun- 
tain, Province of 
Alberta, Canada. A 
huge mass of material 
nearly half a mile 
square, and probably 

400 to 500 feet deep, suddenly slid down the steep face of the 
mountain, into the valley below. The length of the slide was 
about two and a half miles, and it is estimated that the time which 
it took was not more than 100 seconds. The heavy rainfall of 
the preceding year had filled the rock with water, and the earth 
tremors which occurred shortly before the slide are believed to 
have hastened the catastrophe. Extensive mine tunnels at the 
base of the mountain may have aided by making the understruc- 
ture less stable. Many buildings were destroyed, and many lives 
lost. 

Water in the soil and upper rocks works with gravity in the 
extremely slow, down-slope movement of surface material. This 
sort of movement is creep (Fig. 205). It is usually too slow to 
be seen, but it results in the accumulation of mantle rock at the 
bases of slopes. 




Fig. 204. A landslide, 
graph by Hole.) 



(Sketch from photo- 



334 



ELEMENTS OF GEOGRAPHY 



SUMMARY 

From the preceding paragraphs it is apparent that the exist- 
ence and work of ground-water are matters of great importance, 
(i) Without water in the soil most plants could not live, and the 

amount available 
largely controls both 
the density and the 
character of the vege- 
tation. (2) Chiefly 
through its influence 
on plant life, ground- 
water helps to deter- 
mine the distribution 
and occupations of 
people. (3) Ground- 
water is the source of 
all wells and springs. 
Ground-water, seeping 
out, maintains the flow 
of most streams. (4) 
Ground-water may 
modify the character of 
rocks in several ways: 
(a) by removing soluble constituents; (b) by depositing new mate- 
rial in rock cavities; (c) by replacing old material with new; and 
(d) by favoring new chemical combinations. These changes must 




Fig. 205. A ravine near Crawfordsville, In- 
diana, showing trees leaning down-slope, in part 
because of creep. The surface material creeps 
faster than that below, tipping the trees toward the 
axis of the ravine. 




Fig. 206. Diagram of wells on a hill-side. The line below the surface 
represents the water table. 



have occurred on a vast scale, for ground-waters have been at work 
for untold millions of years. As a result, soils and useful ores have 
been accumulated, and igneous and sedimentary rocks "have become 



MODIFICATION OF LAND SURFACES 



335 



metamorphic rocks. (5) The mechanical work of ground- water is 
relatively unimportant, but widespread. The creeping and slump- 
ing of surface material are in some cases due partly to ground-water. 



QUESTIONS 

1. Which of the wells shown in Fig. 206 would you classify as safe, and which 
as unsafe sources of water for domestic use? Why? 

2. In order to contain water constantly, must wells extend farther below 
the surface of the ground on hill tops 

or in valley bottoms? 

3. Make a diagram showing (1) 
the position of the water table during 
the wet and during the dry season, 
and (2) the cross-sections of wells 
which (a) never, (b) occasionally, and 
(c) frequently "go dry." 

4. In order to increase the flow 
of water, dynamite is sometimes ex- 
ploded in wells. Why does this in 
many cases produce the desired effect? 
Would it be more likely to succeed 
with wells penetrating hard, brittle 
rocks, or soft, tough rocks? 

5. Why is it hard in some places 
to get a supply of water in a lime- 
stone country? 

6. Make a diagram showing (1) 
the surface of the ground in a hilly 
region containing a lake, a swamp, 
and a river, and (2) the position of 
the water table beneath this surface 
(a) after continued rains, and (b) dur- 
ing a protracted drought. 

7. What effect does the irriga 7 
tion of arid lands by water led in 
ditches from streams have upon the 
position of the water table? How 
does this affect the question of the 
acreage which ultimately may be 
irrigated? 

8. Why are the inscriptions on 
many old tombstones indistinct? 

9. Describe the characteristics 

of a climate which should (1) hinder, and (2) favor solution by ground- water. 

10. What tilings may have caused the deposition, from solution, of the material 
of the stalactites and stalagmites shown in Fig. 207? 




Fig. 207. The Minaret, Jenolan Caves, 
N. S. W., Australia. The deposits which 
extend downward from the roof of the 
cave, icicle fashion, are stalactites; those 
which are built upward from the floor 
are stalagmites. 



336 ELEMENTS OF GEOGRAPHY 



REFERENCES 

Blatchley: Indiana Caves and Their Fauna, in 21st Ann. Rept., Ind. Geol. 
Surv., pp. 121-212. 

Chamberlin: Requisite and Qualifying Conditions of Artesian Wells, in 
5th Ann. Rept., U. S. Geol. Surv., pp. 131-173. 

Fuller: Underground Waters for Farm Use; Water-Supply Paper No. 255, 
U. S. Geol. Surv. 

Geikie J.: Land Forms Modified by the Action of Underground Water, in 
Earth Sculpture, pp. 266-277. (New York, 1898.) 

Shaler: Caverns and Cavern Life, in Aspects of the Earth, pp. 98-142. (New 
York, 1889.) 

See also general texts mentioned en p. 312. 



The Work of Streams 

Running water is more effective than wind in changing the sur- 
face of the land over which it moves, largely because water is about 
80 times heavier than air. Furthermore, much of the work of run- 
ning water is concentrated in valleys. The work of running water 
is also much more important than that of ice, because water moves 
more readily and affects larger areas. It is true that glaciers have 
been much more extensive than now, at different times in the past, 
but this was the case, so far as known, only for comparatively short 
periods. On the other hand, streams are numerous in most lands, 
and have been for untold ages. Even in deserts few large areas 
are without valleys which contain at least temporary, wet-weather 
streams. All in all, running water is more important than all other 
agents in shaping the details of land surfaces. 

Streams modify land surfaces (1) by moving loose material to 
lower levels, much of it to the sea, (2) by wearing their channels, 
and (3) by depositing their excess loads in various forms. These 
phases of river work, together with their topographic results and 
some of their human relations, are discussed below. The use of 
streams, as for commerce, manufacturing, and irrigation, is discussed 
in Chapter XVI. 

TRANSPORTATION 

Gathering sediment. As rain-water flows down the slopes on 
which it falls, it carries particles of earth to the streams below. 
A stream gets much sediment in this way, if the immediate run-off 
flows over bare, steep slopes of loose material, and little, if it flows 



MODIFICATION OF LAND SURFACES 337 

over slopes well covered with vegetation, such as grass land or forest. 
Water may flow down slope in a sheet, or it may be gathered into 
streamlets. It carries more sediment in the latter case, because 
such water flows faster. Besides the sediment brought to it by 
sheet-wash and temporary streamlets, a stream also gathers mate- 
rial from its bed and banks. 

A stream is not a single, straightforward current. When water 
runs through an open ditch or gutter, some of it may be seen to 
move from sides to center, and some from center to sides, while 
eddies are common. These lesser currents in the main current are 
especially distinct where 

the water flows swiftly. . r 
Streams show the same 
features. These phenom- 
ena show that there are — 
numerous subordinate cur- ^^ITW^ ^ r r^b\ J 

rents in the main current _. _. 

r • 1,1,, , Fig. 208. Diagram to illustrate the effect 

OI a river, and tnat tUey f irregularities, a and b, in a stream's bed, on 
move in various directions. the current striking them. 
Many of them are caused 

by the unevenness of the bed of the stream (Figs. 208 and 209). 
The subordinate upward currents frequently carry sediment up from 
the bottom of the stream, bringing it into suspension. 

Ground- water dissolves rock slowly, and springs bring some 
of this dissolved matter to streams (p. 330). Most dissolved sub- 
stances are invisible, and, unlike mud, remain in the water even 
after it has become quiet. The amount of matter carried to the 
sea in solution each year by all the. rivers of the earth has been 
estimated to be about one-third as much as the sediment carried 
by them (p. 330). 

Carrying sediment. Coarse materials, such as pebbles, in most 
cases are rolled along the bottom, while fine materials, such as mud 
and silt, are likely to be carried in suspension. The movement of 
the coarse materials rolled along the channel is understood easily, 
but the behavior of the fine sediment in suspension needs explanation. 

Mud is composed chiefly of tiny particles of rock, nearly three 
times as heavy as water; hence they tend to sink all the time. But 
as gravity brings them down, many are caught by minor upward 
currents (Fig. 208), and carried up in spite of gravity. It is largely 
by means of these minor upivard currents in the main current, that sedi- 



338 ELEMENTS OF GEOGRAPHY 

ment is kept in suspension. Particles of sediment suspended in a 
stream are dropped and picked up again repeatedly, and the long 
journey of any particle is made up of many short ones. 

Amount of load. The amount of sediment a stream carries 
depends on (i) its swiftness, (2) its volume, and (3) the amount and 
kind of sediment which it can get. Swift and large streams can 
carry a heavier load than slow and small ones. The effect of velocity 
on the carrying power of streams may be seen in most creeks and 
rivers which are wider in some places than in others. Where the 
channel is narrow, the current is swift, and here, in many cases, 
all fine material has been swept away, leaving only pebbles and 
larger stones in the channel. Where the channel is wider, and 
the current slower, the bottom of the same stream may be covered 
with sand or mud. By narrowing the channel of the Mississippi 
by making jetties near one of its mouths, in 1875, James B. Eads 
not only prevented further deposition of sediment there, but forced 
the' river to clear out its own channel. This change permitted 
larger ocean vessels to reach New Orleans at all times. 

The amount of material which certain streams carry to the 
sea has been estimated. For a given river, the estimate is made 
by calculating the average amount of water (in gallons or in cubic 
feet) discharged by it each year, and then determining the average 
amount of sediment in each gallon or each cubic foot. It was esti- 
mated long ago that the Mississippi River carries to the Gulf of 
Mexico more than 400 million tons of sediment each year, an average 
of more than a million tons a day. It would take nearly 900 daily 
trains of 50 cars, each car loaded with 25 tons, to carry an equal 
amount of sand and mud to the Gulf. This sediment represents 
a great loss to the country (p. 267), for most of it would make soil 
of great fertility, if it were on land. All the rivers of the earth are 
carrying perhaps 40 times as much as the Mississippi. 

CORRASION 

How streams wear rocks. As already stated (p. 336), streams 
wear (corrode) their channels. If the channel is muddy, the mov- 
ing water picks up sediment; if sandy or gravelly, sediment is rolled 
along the bottom. Many streams flow on solid rocks, and they 
gather load even from them. Rock exposed to water, as in the bed 
of a stream, decays. As it decays, it crumbles, and the crumbled 
parts are swept away by a swift current. Again, the sand and 



MODIFICATION OF LAND SURFACES 



339 



gravel rolled along by a stream wear its bed even if it is of hard 
rock. Subordinate currents sometimes drive the sediment in suspen- 
sion against the bottom or sides of the channel with similar results. 
The bits of sediment which a stream carries therefore become tools 
(Fig. 209), with which even hard rock is worn away. Clear water, 
flowing over firm, hard rock, effects little mechanical wear. This 




Fig. 209. The tools of a river. Stream-worn pebbles in the bed of the St. 
Joe River, Washington. (Tolman.) 



is shown by the fact that in many cases even large rivers flowing 
from lakes have " mossy" channels. (Why do such rivers have 
few tools?) 

Rate of erosion. The rate at which a stream wears down the 
surface over which it flows depends largely on (1) its volume, and 
this depends chiefly on the amount of precipitation, and on the 
size and configuration of the area draining to it; (2) its velocity, which 
is determined chiefly by its slope, or gradient, and its volume; (3) 
the character of its bed, especially the resistance of its materials; and 
(4) the load which the running water carries. To work most 
effectively, the water must have tools enough to enable it to cut 
rapidly, but not so many that the energy expended in moving them 
retards its flow seriously. Since the factors named above vary 



34Q ELEMENTS OF GEOGRAPHY 

greatly, the rate at which the land is being degraded is very unequal 
in different places. It was calculated recently that the average rate 
of reduction for the United States is about i inch in 760 years; but 
the rate varies from an average of 1 inch of reduction in about 440 
years in the Colorado Basin, to 1 inch in about 3,900 years in the 
basin of the Red River of the North (Fig. 210). 



FEATURES DEVELOPED BY STREAM EROSION 

River Valleys 

The depressions in which rivers flow are their valleys, and in 
the making of valleys streams have been the chief agents. Valleys 
are of much importance to mankind. 

River valleys centers of human activity. Most of the great 
valley lowlands of middle latitudes are settled densely, because 
of their fertile soils, favorable topography, and facilities for com- 
munication. Probably more than one-fourth of the people of east- 
ern United States live on alluvial lands. 

The valleys of the United States have been sought out for set- 
tlement from the beginning of its history. New York history began 
at the mouth of the Hudson, Pennsylvania history in the valley 
of the Delaware, and that of Virginia on the banks of the James. 
Later, various valleys became highways of expansion toward the 
interior. The overflow from the settlements of the coastal low- 
lands of Massachusetts passed over the uplands of crystalline rock 
to the west, to the inviting bottom lands and terraces of the Con- 
necticut Valley. As years passed, this great valley led settlers 
northward into western New Hampshire and Vermont. The lat- 
ter was at first called "New Connecticut," because of the large 
number of settlers who had come from Connecticut. The Ohio 
Valley was one of the first sections of the interior to be settled, and 
for many years the Ohio River was a main highway of westward 
expansion. The upper Rio Grande Valley guided settlers north- 
ward from Mexico into the United States. The Platte Valley 
directed many fur traders and trappers across the Great Plains; 
it was followed by the Mormons on their way to Utah; along it ran 
the Oregon Trail and the first transcontinental railroad; and it 
was the greatest gateway into Nebraska when, in the fifties, the lat- 
ter began to be settled. Many other examples of the role which 
valleys have played in expansion and settlement might be given. 



MODIFICATION OF LAND SURFACES 



34i 



The larger rivers of eastern United States were long the great 
highways of trade and travel. Much of the Interior depended 
almost exclusively on the Mississippi and its tributaries as outlets 
to market, before the building of railroads (p. 420). The latter, 
in many cases, followed the valleys to share in the trade already 
established, but in areas of rough topography, the railroads fol- 
lowed the rivers also because the valley bottoms afforded the easiest 




Fig. 210. Rates of land reduction by stream erosion in the United States. 
The figures are the approximate number of years required for one inch of reduction. 
(Dole and Stabler, U. S. Geol. Surv.) 



grades. In the future, the larger rivers of the United States prob- 
ably will be used more than now to supplement railroad transpor- 
tation (p. 438). 

Many valleys are grown-up gullies. Many valleys are en- 
larged gullies. A gully started during one shower (Fig. 211) is made 
deeper, wider, and longer by the next. As the result of repeated 
showers year after year and, in many places, repeated meltings 
of snows, the gully grows to be a ravine, and later a valley. Not 
all gullies, however, become valleys. Many gullies may start on 
a slope (Fig. 212), but as they grow, some are so widened as to take 
in others (Fig. 213), and the number is reduced. As gullies develop, 
the heads of some work back faster than others (Why?), with the 
result that many valleys are arrested early in their development, 



342 



ELEMENTS OF GEOGRAPHY 




as shown in Fig. 212. But a small proportion of all that start become 
ravines, fewer still become small valleys, and the number of valleys 

which attain great 
length is very small. 

Growth of gullies 
should be prevented. 
Much land in the 
United States has 
been ruined (Fig. 214) 
and much more in- 
jured, for agricultural 
purposes, by the for- 
mation of gullies.. 
There are many ex- 
amples of such land 
in the southern Ap- 
palachians, where, on 
unprotected surfaces, 
gullies form and grow 
rapidly because the 
slopes are steep, the 
rainfall heavy, and much of the surface material is eroded easily. 
Surfaces of this sort should, as a rule, be kept covered with trees, 

and given over to the 
growth of forests. But 
serious gullying is by 
no means confined to 
mountain areas (Fig. 
215). Indeed, the 
problem of checking 
the growth of gullies is 
country-wide. They 
can be controlled best 
while still small. One 
way of doing this is by 
filling them with brush 
(Fig. 216). Fig. 217 
shows one method of restraining the water of mountain torrents. 

How valleys get streams. Water commonly flows in gul- 
lies only when it rains or when snow melts, and for a short time 



Fig. 211. A gully developed by a single shower. 




Fig. 212. Gullies on slope above a valley flat. 



MODIFICATION OF LAND SURFACES 



343 



afterward; their active growth is therefore intermittent. But many- 
valleys made from gullies have permanent streams, so that their 
enlargement goes on all 



..__ c. 



5^._ _.. 




the time. 

When a valley has 
been deepened so that 
its bottom is below the 
ground-water surface, 
ground-water seeps or 
flows into it, and forms 
a stream. In Fig. 218, a 

represents the water surface in wet weather, and b the water surface 
in dry weather. The valley whose cross-section is shown by 1 does 
not have a stream derived from ground- water ; the valley 2 has a 



Fig. 213. Diagram illustrating how one gully 
takes another as a result of lateral erosion . 




Fig. 214. Typical old-field erosion, near Grand Junction, Tennessee. 
U. S. Bureau of Soils.) 



(McGee, 



small stream in wet weather; while the valley 3 has a permanent 
stream, because it is below the ground-water level of dry time. 

Streams which are fed by lakes, and streams which have their 
sources in snow- and ice-fields which last from year to year, do not 
depend on ground-water, though in most cases they receive it. 



344 



ELEMENTS OF GEOGRAPHY 



The deepening of valleys. Swift streams remove material from 
their beds and so make their valleys deeper, but many slow streams 










Fig. 215. Gullying in southwestern Iowa. (Iowa State Drainage, Waterways, 
and Conservation Commission.) 

deposit more sediment than they take away, and so make their valleys 
shallower. Many streams deepen their valleys in their upper courses 

where their waters are 
swift, while they make 
them shallower in 
their lower courses 
where the flow is slug- 
gish. As a stream 
deepens its valley, the 
gradient becomes less, 
and the stream flows 
more and more slowly. 
In time, every swift 
stream will cut its 
channel down until its 
gradient is low and 
its current sluggish. A 
stream cuts the lower 
end of its channel down 
to about the level of 
the lake, sea, or river in- 








Fig. 216. Brush dams built to check erosion in 
the southern Appalachians. 



to which it flows, but the channel rises from its lower end to its head. 
The lowest level to which a stream can reduce its basin is base-level. 



MODIFICATION OF LAND SURFACES 



345 



The widening of valleys. Valleys are widened in many ways, 
among them the following: (i) A stream may flow against one 
side of its channel with such force as to undercut the slope above 
(Fig. 219). Slow streams are more likely to widen their valleys in 
this way than swift ones, 
because they are turned 
more easily against their 
banks by obstacles in 
the channels. (2) Rain- 
water flowing down the 
slopes of a valley carries 
earthy material with it. 
This widens the valley, 
by slowly wearing back 
its slopes. (3) The loose 
matter which lies on the 
slopes of a valley creeps 
slowly downward, espe- 
cially when wet. It may 
also slump down steep 
slopes. In these and 
other ways, all valleys 
are being widened all 
the time. At the bases 
of the slopes of many 
valleys there is much 
talus waiting to be car- 
ried away by the stream. 

After, streams have 
cut their valleys down 
to low gradients, they 
make flats in their bot- 
toms, by side-cutting (Fig. 220). These flats are below the level of 
the surface in which the valleys lie, and may become very wide. 
Thus the Mississippi River at Dubuque has a flat between one 
and two miles wide, and about 600 feet above sea-level. Near St. 
Louis the fiat is 10 miles wide, and about 400 feet above sea-level. 
At Memphis it is about 35 miles wide, and only 220 feet above 
the sea. At Vicksburg it has a similar width, and a height of but 
90 feet. Normally, valley flats increase in width more or less 




Fig. 217. A method of restraining the water of 
mountain torrents, to prevent the carrying away 
of the soil. Savoie, France. (Kuss.) 



M/ 



_ b 



346 ELEMENTS OF GEOGRAPHY 

regularly down stream (Why?). Figs. 221 and 222 show valley flats 
of different widths. 

The lengthening of vafleys. The headward growth of a gully 
is due chiefly to erosion by the water which flows into its upper 
end. The head of a gully advances in the direction of greatest 
wear, and this is rarely in a straight line, for more water flows in at 
the head, now from one direction, and now from another. Again, 
the soil or rock in which a gully is cut may be harder at some points 
than at others, and the head of the gully is likely to advance on that 

which is worn most 

easily. Most valleys 

3 are therefore crooked 

from the outset. 

The headward 

growth of a valley nor- 
Fig. 218. Diagram showing ground-water sur- „ t - t -i 

face; a, the ground- water surface at ordinary times, mall y continues until 
and b, in times of drought. When a valley has been the erosion accom- 
cut below a, there will be a stream in wet weather, pfished by the water 
but it will go dry in time of drought. When the val- K . . 
ley bottom is below b, the stream will be permanent. flowing into Its upper 

end is equaled by the 
wear of the water flowing from the same divide (water-parting) in 
the opposite direction. The divide is then permanent (Fig. 223). 

Valleys are not all grown-up gullies. Not all valleys were 
formed by the growth of gullies. A vast area in northern North 
America, for example, once was covered by a sheet of snow and 
ice. Most of the rivers which had existed in this area ceased to 
flow while the ice lay on the land. Many of their valleys were 
filled, at least in places, by the drift which the ice left when it melted. 
The result was that great areas were left without well-defined 
valleys. The melting ice, however, supplied quantities of water, 
and this flowed along the lowest lines of descent which it could 
reach, and developed valleys along those lines. Valleys developed 
by such waters may have permanent streams at the start, since 
they do not depend on ground- water. 

Again, the melting of the ice left many lakes in the hollows of 
the land it had covered, and the rainfall of the region was great 
enough to make many of them overflow. When a lake overflows, 
the out-going water follows the lowest line of descent, and cuts 
out a valley. In these ways, rivers soon were re-established on 
the surface from which the ice melted. 



MODIFICATION OF LAND SURFACES 



347 



Valley and river systems. Most valleys are joined by many 
smaller tributary valleys. The reason is simple. The erosion 
of the slopes of valleys by the water flowing from them to the valley- 




Fig. 219. The Belle Fourche River undercutting its banks. (Darton, U. S. 
Geol. Surv.) 



bottoms is greater along some lines than others (Why?), and tribu- 
tary gullies are started, which, growing in the same way as the parent 
valleys, may come to have permanent streams. These tributary 



348 



ELEMENTS OF GEOGRAPHY 





valleys of the first generation develop branches, and the process 
may go on until a network of watercourses affects the surface. 

A valley and its tributaries con- 
stitute a valley system. A stream 
and its branches form a river sys- 
tem, and the area drained by a river 
system is a drainage basin. 

Stages in the history of valleys 
and streams. Valleys grow in size 
as they advance in years. When 
a valley is young, it is narrow, and 
its slopes are steep. If the land 
is high, the valley may' have a 
steep gradient, in which case it 
soon becomes deep. Its cross-sec- 
tion is then somewhat V-shaped 
(Fig. 224, 1), and its tributaries 
are short. A mature valley is wider 
(Fig. 224, 2), its slopes in most 
cases are gentler (Fig. 225), and its 
tributaries are longer and older. 
An old valley is wide, and has a 
broad flat and a low gradient (Fig. 
224, 3). 

Fig. 220. Diagrams of a river A stream als0 > aS Wel1 aS its val " 

developing a flat by side cutting. ley, passes from youth to maturity, 













Fig. 221. Gray Copper Gulch, southwestern Colorado. 



MODIFICATION OF LAND SURFACES 



349 



and from maturity to old age. In its youth, it is likely to be swift, 
unless it flows through low land. In maturity, it flows less swiftly 




Fig. 222. A wide valley flat. Milk River, near the Montana- Alberta 
boundary. (From photograph by U. S. Geol. Surv.) 



Fig. 223. Diagram of a divide. 
The crest of the divide (at A) is per- 
manent if the conditions of erosion 
are the same on the two sides. Rain- 
fall may lower it, but cannot shift 
its position horizontally. 



and more steadily, and when it 
reaches old age, it winds slowly 
through its wide plain. Even an 
old stream, however, may take on 
the vigor of youth when in flood. 

The terms youth, maturity, and 
old age may be applied to river 
systems as well as to single rivers. 
Every river system, aided by weath- 
ering, has entered on the task of 
carrying to the sea all the land of 
its basin which is above base-level. 
So long as the river system has the 
larger part of its task before it, it 
is young. When the main valleys 
have become wide and deep, and 
the areas of upland have been well 

dissected by valleys, the river system is said to have reached 
maturity. When the task of reducing its drainage basin to base- 




Fig. 224. Diagram showing 
changes in the shape of a valley as 
it advances from youth to old age. 
1 = youth; 3 = old age. The 
material in which the valley is cut 
is all of the same character. 



350 ELEMENTS OF GEOGRAPHY 

level is nearing completion, the river system has reached old age. 
The main stream of a drainage system attains the characteristics 
of maturity and old age sooner than its tributaries, and in its lower 
course sooner than in its upper. 

The topography of a drainage basin is youthful when its river 
system is youthful, mature when its river system is mature, and 
old when its drainage is old. In an area of youthful topography, 
much of the surface has not yet been much changed by erosion 
(Fig. 226), and the surface may be ill-drained. In an area of mature 




Fig. 225. A mature valley slope. Cobb's Creek, near Philadelphia, Penn- 
sylvania. 

topography, much of the surface has been reduced to slopes by ero- 
sion (Fig. 227), and is well-drained; while an area of old topography 
is one which has been brought down to general flatness by erosion 
(Fig. 228). Those parts of a drainage basin near the main stream 
may take on the characteristics of old age, while other parts farther 
from the trunk stream are not advanced beyond maturity, or even 
youth. 

When an area is worn as low as running water can bring it, it 
is a base-level plain. As streams wear the land toward base-level, 
they flow on diminishing gradients. Because of this, their velocity 
and therefore their erosive power decrease constantly. In other 
words, an area approaches base-level more and more slowly the 
nearer it gets to it, and it may take as long to wear away the last 
few feet above base-level as it did all the other hundreds or thou- 
sands of feet that once lay above. . Few, if any, areas have been 
absolutely base-leveled. The time required is enormous, and before 
the task is completed, an area is likely to be elevated with reference 



MODIFICATION OF LAND SURFACES 



35i 



to sea-level, and the quickened rivers started upon the task of again 
reducing the elevated land to base-level. But many areas have 
been nearly base-leveled. Such plains are peneplains (almost plains) . 
Above their otherwise nearly level surface, occasional elevations may 
rise abruptly. These elevations, known as monadnocks (Fig. 229), 




Fig. 226. Diagram of an area in a youthful stage of erosion. The area is 
some distance from the sea. The bottom of the diagram represents sea-level. 




Fig. 227. Diagram showing mature topography in a region situated some 
distance from the sea. The bottom of the diagram is sea-level. The area shown 
in Fig. 226 will in time resemble closely the present appearance of this area. 




Fig. 228. Diagram showing old topography in a region situated some distance 
from the sea. The bottom of the diagram is sea-level. Unless the land is elevated, 
the areas represented in the two preceding figures will finally closely resemble this 
area. 



352 ELEMENTS OF GEOGRAPHY 

owe their existence to (i) the greater resistance of their rocks, or 
(2) a favorable position among drainage lines. The time required 
for reducing a drainage basin to a base-level plain, is a cycle of erosion. 
As implied above, cycles of erosion commonly are brought to an 
end by relative uplift of the land before they are completed. 

The terms youth, maturity, and old age, as used in geography, 
apply to stages of development, and not to periods of years. Thus 
a small river, working on soft material, may bring its valley to old 
age in less time than that required for a large stream, opposed by 
resistant rocks, to bring its valley to maturity. 

Influence of stage of erosion on human activities. The den- 
sity of population of a region and the condition and activities of 
its people are influenced greatly by the stage which it has reached, 
in its topographic development. Many young rivers are inter- 
rupted by falls and rapids (p. 356) which afford water power for 
manufacturing, but interrupt or prevent navigation. Many young 




Fig. 229. A monadnock on the Canadian peneplain. Tower, Minnesota. 
(Mead.) 

rivers, too, are not available for commerce, partly because they 
flow in narrow valleys, far below the level of the surrounding coun- 
try. In parts of western United States, it is also impracticable to lift 
the waters of such streams to the neighboring uplands for purposes 
of irrigation. Thus the waters of the Colorado River can be used 
for irrigation only in the upper part of the river system, or below 
the Grand Canyon, and the larger irrigation projects of southern 
Idaho are related definitely to breaks in the walls of the deep canyon 
of the Snake River. Again, very deep valleys may make travel 
across their courses almost impossible. In such cases, places where 



MODIFICATION OF LAND SURFACES 353 

the valleys can be crossed may have all the significance of mountain 
passes, controlling the courses of trails and roads. The Denver and 
Rio Grande Railroad crosses the Green River in eastern Utah where 
there is a gap in the canyon wall, a gap that earlier determined the 
course of the Spanish Trail. Roads may run in any direction over 
young plains whose valleys are shallow. Practically all the land of 
such plains is available for agriculture, so far as topography is con- 
cerned. The poorly drained inter-stream flats may require extensive 
ditching or tile draining, however, as in parts of Iowa and Illinois. 

Where relief is great, the mature stage of erosion is least favor- 
able to most human activities. The larger rivers may be navigable, 
but most of their tributaries are likely to have steep gradients, with 
falls and rapids. At this stage, run-off is at a maximum, and streams 
are most subject to floods. Many of the larger rivers are crossed 
at occasional ferries and fords, for bridges are hard to maintain. 
Good sites for river towns also may be few. Wagon roads and rail- 
roads follow the narrow ridges between the valleys, or the flats of 
the larger streams. Farming is difficult on the steep valley slopes, 
where soils are likely to be thin and easily washed away. In gen- 
eral, the population of such regions is sparse and non-progressive, 
having little contact with the outside world. Mineral deposits or 
other special resources may create industrial centers, whose progress 
serves to emphasize the backwardness of the region as a whole. 
These conditions are illustrated in parts of the Cumberland and 
Alleghany plateaus (p. 275). 

Old rivers are, as a rule, free from rapids and falls, and in most 
cases have gradients so gentle that they do not afford good water 
power. While these conditions favor navigation, the latter may 
be interfered with by sand bars (p. 364) and the shifting and crooked 
courses of the channels. It is nearly a thousand miles from Cairo, 
at the mouth of the Ohio River, to New Orleans by way of the Mis- 
sissippi River, but only about half as far in a straight line. Much 
of the land of the broad flood-plains of old rivers is swampy and 
unavailable until drained, but is then of great fertility (Why?) . While 
floods are most numerous in valleys whose slopes are steep, they 
are more likely to be disastrous to property on the broad, low flats 
of older rivers, such as the lower Mississippi (p. 366). On the gentle 
inter-valley slopes of an old area, the soils are likely to be deep 
(Why?) ; their fertility depends chiefly on the character of the under- 
lying rock. The area of arable land is, as a rule, much greater in topo- 



354 



ELEMENTS OF GEOGRAPHY 



graphic old age than in maturity. On peneplains, as on youthful 
plains of low relief, communication is easy in all directions. Wagon 
roads and railroads are not confined to certain courses by topography. 
Canyons and gorges. Valleys which are narrow and deep 
are often called gorges if small, and canyons if large. The Colorado 
Canyon (Fig. 230) is the greatest canyon known. Its depth is 




Fig. 230. Inner gorge (canyon) of the Grand Canyon of the Colorado, Arizona. 
(Walcott, U. S. Geol. Surv.) - 



about a mile, and it is eight to ten miles wide at the top. Its sides 
are step-like, because of the unequal hardness of the rock of the 
canyon walls. The harder strata are the cliff-makers. The Yellow- 
stone (Fig. 231), Snake, and Columbia rivers have wonderful can- 
yons in some parts of their courses, and so has the Arkansas River 
where it flows through the Rocky Mountains. The canyons of many 
smaller and less well-known rivers are almost equally striking. 

A narrow valley means that the processes which have made 
it deep have outrun the processes tending to make it wide. Val- 
leys are deepened rapidly when their gradients are high and their 



MODIFICATION OF LAND SURFACES 



355 



streams strong. They are widened slowly (i) when the climate 
is arid, so that there is little slope wash, (2) when the stream is 
so 'swift that it does not meander, and (3) when the material of the 
sides is such that it will stand with steep slopes. We conclude, 
therefore, that (1) great altitude, (2) arid climate, (3) swift streams, 
and (4) rock which will stand in steep slopes, favor the development 




Fig. 231. The canyon of the Yellowstone. (Hillers, U. S. Geol. Surv.) 



of canyons. In other words, young valleys in plateaus and moun- 
tains (as in western United States) are likely to be canyons. (How 
can there be large, strong streams in dry regions?) 

Some of the ancient cliff-dwellers made their homes in the 
recesses of canyon walls (Fig. 232), probably because these posi- 
tions could be defended easily. 

Canyons must develop into valleys of another type, for the stream 
in the canyon will in time cut down to its base-level. The valley 
will then stop growing deeper, but widening will still go on, and the 
narrow valley will become so wide that it will cease to be a canyon. 



356 



ELEMENTS OF GEOGRAPHY 



Rapids and falls. The bed of a stream may be steeper at 
some points than at others, and there the stream flows more rapidly. 

The quickened flow 
constitutes a rapids 

(Fig- 233); or > ^ the 
water in a stream's bed 
drops over a cliff, it 
makes a waterfall (Figs. 
234 and 135). Water- 
falls and rapids are 
important chiefly be- 
cause they render the 
power of the streams 
available to man for 

Fig. 23 2. Cliff dwellings, southwestern Colorado. Ptoses of manufac- 
turing, lighting, trans- 
portation, etc. (p. 440). Many electric railroads and many industries 
depend for power on electricity developed by falls and rapids, and 





Fig. 233. Rapids in the Kootenay River, British Columbia. 



MODIFICATION OF LAND SURFACES 



357 



railroads and factories of all sorts are likely to depend on this sort 
of power stiH more largely in the future. Rapids and falls interfere 
with navigation, or prevent it 
altogether (p. 352). 

Waterfalls come into exist- 
ence in various ways. A river 
flowing on the high gradient 
shown in Fig. 235 is likely to be 
an eroding river. It will wear 
its channel faster at A , where the 
rocks are soft, than just above, 
where they are hard, with the 
result shown in Fig. 236. The 
continued wear of the water in 
such a case would cause the 
rapids at A (Fig. 236) to be- 
come steeper, and in time the 
descending water would become 
a fall (Fig. 237). In this case, 
the rapids and falls depend on 
inequalities of hardness in the bed 
of the stream. This is a common 
way in which falls and rapids 
originate. A landslide or lava 
flow may form a dam, over 
which the water falls or flows in 
rapids. Most of the waterfalls 
of the United States are due to 
glaciation (pp. 393, 405). 

Falls and rapids are under- 
going constant change, although 
the change is usually very slow. 
Many falls are moving slowly 
up-stream, because the water 
undermines the hard layer of rock over which it drops (Fig. 237). 
As a fall recedes, it becomes lower in many cases (Fig. 237). It is 
clear that such falls will disappear if they recede far enough. If 
the hard rock over which the water drops is in the position shown 
in Fig. 238, the fall will not recede, though it will become lower, 
and will disappear when the stream cuts down to base-level, where 




Fig. 234. Falls of the Black River, 
Wisconsin. (Smith, Wis. Geol. Surv.) 



358 



ELEMENTS OF GEOGRAPHY 



the fall is. (What would be the effect of re-elevation of the basin?) 
Rapids and falls are temporary features of streams, and, like can- 
yons, are marks of youth. In time, therefore, all existing rapids and 
waterfalls will disappear. 

Narrows. Many valleys are narrow where they cross a tilted 
layer of hard rock. Such $, constriction of a valley is a narrows, 




Fig. 237. 

Figs. 235, 236, 237. Diagrams to illustrate the development and extinction 
of a waterfall. 

Why will the waterfall cease to retreat up-stream when it reaches C-B, Fig. 
237? What changes will occur after it reaches this place? 

or water-gap (Fig. 239). The Delaware Water-Gap through 
Kittatinny Mountain (Pa.-N. J.) is a well-known example. Unlike 
falls, narrows are not most conspicuous in the youth of the stream, 
but later, after the valley has been much widened except where it 
crosses the hard rock. Falls are common in horizontal or nearly 
horizontal beds, but most narrows are developed in tilted beds. 

Narrows sometimes serve as gateways through mountains, and 



MODIFICATION OF LAND SURFACES 



359 



so control lines of travel. The narrows of Wills Creek in Wills 
Mountain, Maryland, may serve as an example. In the early 
days of American history, Fort Cumberland was built at this nar- 
rows to guard the important pass through the mountains, and Wash- 
ington's and Braddock's roads ran west 
through it. At the present time, the 
Cumberland National Road and an im- 
portant railway make use of it. 

Accidents to streams. Streams are 
subject to many accidents. If the land 
through which they flow sinks so that its 
slope is reduced, they flow less rapidly, 
or may even cease to flow. If the lower 
end of a valley sinks below sea-level, the 
sea-water enters and forms a bay, drowning the lower end of the 
river and its valley. If the streams along a coast end in bays, we 
infer that the coast has sunk, and that its rivers and valleys have 
been drowned. Thus Delaware Bay, Chesapeake Bay, and numer- 
ous other smaller bays between New York and the Carolinas ar*e 
drowned valleys. 

These submerged valleys of the Atlantic coast form part of a 
great "Inland Waterway" which, interrupted by land in only four 




Fig. 238. Diagram of water- 
falls developed on vertical beds. 




Fig. 239. Lower Narrows of the Baraboo River, Wisconsin. The valley 
widens beyond the gap, the same as in the foreground. 



places, extends from Boston to South Caroliha (Fig. 322). An active 
intercolonial trade was carried on along this route. Parts of it were 
important in the operations of the Revolutionary War and the 
War of 181 2. Later, canals were constructed between the Raritan 
and Delaware rivers, between Delaware and Chesapeake bays, 




360 ELEMENTS OF GEOGRAPHY 

and between the lower Chesapeake Bay and Albemarle Sound (Fig. 
317). These canals are all comparatively shallow, and have been of 
little importance for years. Deep, modern canals probably will 
replace them in the near future (p. 439). 

If the basin of an old stream is raised so that the gradient of the 
stream becomes greater, its velocity is increased, and it again takes 

on the characteristics of youth. 
^Z^^-C^^^. s^ : " ;| Such streams are said to be re- 
--fC^^ii^' 5 ^ ^gJ|R juvenated. 

^'^"^ U If by headward growth one 

valley reaches and enters another 
where the latter is at a higher level, 
it may steal the water which other- 
wise would flow down the higher 
valley (Figs. 240 and 241). The 
Figs. 240, 241. Diagrams to stream which steals is a pirate. 
illustrate stream piracy. The stream stolen is diverted, and 

the stream which has lost its upper 
water is beheaded. Piracy has been rather common among rivers, 
especially in mountain regions. In the Appalachian region, for 
example, there are few large streams which have not either increased 
their waters by piracy, or suffered loss by the piracy of others. 
Piracy is favored by inequalities of hardness, for streams which do 
not cross hard rock deepen their channels more readily than those 
which do (Fig. 242). 

When a stream is diverted from a narrows, the water-gap becomes 
a wind-gap. Wind-gaps are common in most mountain regions 
which have advanced to late maturity. Cumberland Gap, in the 
southeastern corner of Kentucky, is an example (Fig. 243). It 
afforded many of the early emigrants the most available route across 
the mountains, and during the last quarter of the eighteenth century 
probably more than 300,000 people passed through it to settle in 
the West. The numerous wind-gaps of the Blue Ridge Mountains 
figured prominently in the early westward movement of population, 
and again in the campaigns of the Civil War. 

DEPOSITION BY STREAMS 

Causes of deposition. Streams may become overloaded in 
various ways, and so be forced to deposit their excess sediment: 
(1) Their carrying power may be reduced by a decrease of gradient. 



MODIFICATION OF LAND SURFACES 



361 



The change may take place suddenly, as at the base of a steep slope, 
or when a river enters a lake or the sea ; or it may take place slowly, 
as a stream flows through a valley whose slope becomes gradually 
less. (2) Their carrying power may be diminished by decrease of 
volume. Streams flowing through arid regions may receive little 
water, and lose much by evaporation and by absorption into the 




Fig. 242. A case of stream piracy in Pennsylvania. The upper part of the 
present Wiconisco Creek formerly was tributary to Deep Creek, joining the 
latter at "A." (From Millersburg and Lykens, Pennsylvania, Sheets; U. S. 
Geol. Surv.) 

What enabled Wiconisco Creek to behead Deep Creek? What was the prob- 
able origin of the mountain gap at "B"? Is future piracy likely to occur in this 
region? Why? 



dry earth. Many streams in the West leave the mountains bank- 
full, to wither and disappear on the lower lands. Many also have 
much of their water withdrawn for purposes of irrigation. (3) 
Tributary streams with high gradients may bring to the main streams 
more sediment than the latter can carry away. 

Deposits at the bases of steep slopes. Every shower washes 
fine sediment down the slopes of hills and mountains, and much of 
it is left at their bases, where the velocity of the water is checked 
suddenly. At the lower end of every new-made gully on a hillside, 
there is a mass of debris which was washed out of the gully itself 
(Fig. 211). Material in such positions accumulates in the form 
of an alluvial cone, or a gentler sloping alluvial fan (Fig. 244). The 
rivers descending from the Sierras to the valley of California have 



362 



ELEMENTS OF GEOGRAPHY 




MODIFICATION OF LAND SURFACES 



363 



built great fans along the foot of the range, and most of the rivers 
coming out of the Rockies to the plains east of them have done the 
same thing. Many of the fans of streams descending from the 
western mountains are miles across. Fans made by neighboring 
streams may grow until they unite to form a compound alluvial fan, 
or a piedmont alluvial plain (Fig. 245). Such plains exist at the 




Fig. 244. Alluvial fan at the mouth of Aztec Gulch, southwestern Colorado. 
(U. S. Geol. Surv.) 



bases of most considerable mountain ranges. Their alluvial depos- 
its may be hundreds of feet thick. 

Many alluvial fans and piedmont alluvial plains are valuable 
for farming. (In general, which would be more valuable, the higher 
or the lower portions of alluvial fans? Why?) In parts of southern 
California, for example, such lands are so valuable that farms are 
very small and highly improved (Fig. 246). Water is supplied (1) 
by wells, through which the debris of the fan is made to yield up the 
water it has absorbed, or (2) by irrigating ditches which connect 
with a stream or reservoir at a greater height. To save more of the 
flood waters of the Santa Ana River, the principal stream in the 
citrus fruit region near Los Angeles, provision was made recently 
for turning a portion of them out of the channel upon the upper 



364 



ELEMENTS OF GEOGRAPHY 



part of the great alluvial fan of the Santa Ana, where, to increase 
absorption, dikes were thrown up and hundreds of ponds created. 
Seeping through the porous sand and gravel, this water joins the 
great artesian reservoir of the region. As a result of this measure 
and of keeping the artesian wells capped when not in use, the water 
table of the basin has risen one foot, in spite of the ever increasing 
demand for water. This means an addition of more than 100,000 

acre-feet 1 of water. At 
half the current price, 
this amount of water 
has a value of about 
$200,000. In many 
parts of the West, allu- 
vial fans and cones will 
be used increasingly in 
the future for the 
storage of storm- 
waters. Many villages 
in mountain valleys 
are situated on alluvial 
fans. The agricultural 
settlements of Utah 
spread southward from 
the vicinity of Great 
Salt Lake along the piedmont alluvial plain at the west base of the 
Wasatch Mountains. (Why the west base of the mountains?) 
Most of the cities and villages of the state are within this belt. 

Deposits in valley bottoms; conditions on flood-plains. The 
gradient of a stream generally becomes less toward the mouth, and 
so it happens that sediment is distributed for great distances along 
valley bottoms. Some of it is left in the channels, and some is 
spread over the low lands along the streams, making alluvial plains 
(Fig. 247). 

Streams sometimes deposit sand bars in their channels (Fig. 248), especially 
in low water. Bars and the tree trunks and snags which they often catch and 
hold, interfere with navigation, especially when the rivers are low. In earlier 
years, many steamboats were wrecked on such obstructions on the Missouri 
and lower Mississippi rivers. It has been estimated that 70% of all steamboat 
losses on the Missouri were due to snags. Scarcely was the steamboat established 

*An acre-foot is water enough to cover one acre to the depth of one foot. 













j^S^^f^^^^i^"' ^^■ ¥vK ^^'^f^ s 




w^tJS^t-.- •jjp'" *WS^P4HHp( 


91 




§ 


jlj^jjfeV; v -_\ ./- - _- : ';"'V-' J 



Fig. 245. Piedmont alluvial plain east of Sierra 
Nevada Mountains, California. (Fairbanks.) 



MODIFICATION OF LAND SURFACES 



365 



on the western waters before demand was made that the federal government 
undertake the removal of snags and the dredging of channels. The West had 
become so powerful a factor in national affairs that it soon obtained the assistance 
it demanded. In beginning the improvement of western streams, the govern- 
ment accepted the task of fostering internal as well as ocean commerce. In 1824 
Congress provided for the first improvements on the lower Mississippi and Ohio 
rivers. By 1839, 10,000 stumps and snags had been removed from the Ohio alone. 




Fig. 246. Cultivated alluvial fan near Riverside, California. 



Alluvial plains along large rivers are almost flat, though they 
slope gently down-stream, and many of them have natural levees. 
This term is applied to the low ridges along the banks of the channel 
(Fig. 249). In times of flood, the current in the main channel is 
swift; but so soon as the water spreads beyond its channel, its velocity 
is checked because its depth suddenly becomes less, and it promptly 
abandons much of its load. During the period of overflow, the edges 
of the channel current are checked by the slower moving flood-plain 
water, and this causes further deposition on the banks of the channel. 
Repeated deposition in this position gives rise to levees. Embank- 
ments have been built by man upon the natural levees of some 
rivers to prevent the flooding of the valley flats, and to make the 
bottom lands available for settlement. Louisiana alone has spent 



3 66 



ELEMENTS OF GEOGRAPHY 



more than $35,000,000 since 1865 in levee building, and is expending 
now about $800,000 a year in this way. (Why must the protective 
levees be built higher and higher as time passes?) In spite of such 




Fig. 247. A portion of the flood-plain of the Illinois River. 

improvements, floods are unfortunately frequent. The damage 
which they did to buildings, bridges (Figs. 250 and 251), railroads 
(Fig. 252), etc., in the United States in 1908 was estimated at more 




Fig. 248. "Fish hook" sandbar in Little Missouri River, Clark County, 
Arkansas. (Veatch, U. S. Geol. Surv.) 



MODIFICATION OF LAND SURFACES 



367 



than $237,000,000, though not all this damage was done on the 
flood-plains of large rivers. Impressive as this estimate is, it takes 
no account of the great damage done to the land itself (Fig. 144), 
nor is it possible to 
measure the suffering 
and reduced efficiency 
of the people living in 
districts that have been 
visited by great floods. 
Most of the early 
population of Louis- 
iana and Mississippi 
was distributed in narrow belts along the levees of the Mississippi 
and its branches. The land here was high enough and dry enough 
to be cultivated, very fertile, and close to the streams which were 
the great highways of that time. The plantations were narrow 
along the streams, and extended back at right angles to them until 
the land became too low and wet for cultivation. 




Fig. 249. Diagram showing natural levees. 




Fig. 250. Railway bridge over the Nolichucky River at Unaka Springs> 
Tennessee. (Glenn, U. S. Geol. Surv.) 



3 68 



ELEMENTS OF GEOGRAPHY 



A stream in an alluvial plain is likely to wind about, or meander 
(Fig. 253). This is the result of the low velocity of such a stream, 
for sluggish streams are turned aside easily. Were such a stream 
made straight, it would become crooked again, for the banks of all 
streams are less firm at some places than at others, and the stream 




Fig. 251. Same place as shown in Fig. 250 after the bridge and piers were 
swept away by the flood of May, 1901. (Glenn, U. S. Geol. Surv.) 



would cut more at those places. If the shape of the channel were 
such as to direct a current against a given place in the bank, the 
result would be the same, even without difference of material. If a 
curve in the bank is once started, it is increased by the current 
which is directed into it, and, as the current comes out of a curve, 
it is projected against the opposite bank, and develops a curve on 
that side. The water issuing from this curve tends to make another, 
and so on. Once started, meanders tend to become more and more 
pronounced (Fig. 254) until, probably in some time of flood, the stream 
cuts through the neck of the meander and straightens its course. 



MODIFICATION OF LAND SURFACES 



369 



When a stream has cut off a meander, the abandoned part of the 
channel may remain for a time unfilled with sediment. If it contains 
standing water, it becomes the site of an oxbow lake or bayou (Fig. 253). 




Fig. 252. Scene in freight yards at Kansas City after the flood of 1903. 
photograph by U. S. Weather Bureau.) 



(From 



The many sloughs, bayous, and swamps of the Mississippi flood-plain inter- 
fered greatly with the movements of the Union armies before Vicksburg. Unsuc- 
cessful attempts were made by the Northern commanders in 1862 and again 
in 1863 to straighten the river by 
cutting a canal between "A" and 
"B," Fig. 255. Had they succeeded, 
Vicksburg would have been left on 
an oxbow lake at some distance from 
the main channel, and would have 
lost its control over the river. In 
1876, the river itself cut off the mean- 
der (Fig. 256), to the great injury of 
Vicksburg. 

Fig. 253. The Rio Grande near Browns- 

In meandering, a stream v ille, Texas. 

sometimes reaches and under- 
mines the valley bluff, thus widening its valley flat. This is, indeed, 
the most important process in the widening of valley flats (p. 345). 
Towns grew up early on the bluffs of the lower Mississippi at points 




37<> 



ELEMENTS OF GEOGRAPHY 



where the river touched the side of its valley. In this way the loca- 
tion of Natchez, Vicksburg, Memphis, and other places was deter- 
mined. Such defensible sites, overlooking and dominating the 
river, were bones of contention between Spain and the United States 

during the dispute over the southwest- 
ern boundary, from 1783 to 1795. The 
same physiographic features located the 
Confederate defenses of the Civil War 
at Columbus (Ky.), Ft. Pillow (Tenn.), 
Vicksburg (Miss.), Grand Gulf (Miss.), 
and Port Hudson (La.).. 

By shifting their courses, as the 
result of deposition and meandering, 
streams have affected human interests in many other ways. Vil- 
lages which grew up on the banks of navigable rivers, because of 
the river trade, in some cases have been left far from the streams 
by changes in the positions of the latter. Such villages usually 




Fig. 254. Diagram showing 
development of a meander. 





Fig. 255. Fig. 256. 

Fig. 255. Sketch-map of Mississippi River at Vicksburg at time of Civil War. 
Fig. 256. Course of Mississippi River at Vicksburg in 1896. 



decline when the streams withdraw- their patronage. Other places 
built on river banks have been preserved at great expense, while 
some have been washed away. The Mississippi River flows over 
the site of Kaskaskia, one of the most important French settle- 
ments in the upper Mississippi Valley, and the first capital of 
Illinois. The Missouri River destroyed Franklin, Missouri, an out- 



MODIFICATION OF LAND SURFACES 371 

fitting place in the 1820's for the trade across the Great Plains 
to Santa Fe. 

Many streams have been used as boundaries between counties 
and states. In numerous cases the shifting of the stream has led 
to boundary disputes, for, by the cutting off of meanders, tracts of 
land have been shifted from one state to another. In the case of 
the Missouri River, there have been disputes between Nebraska 
and South Dakota, Nebraska and Iowa, and Nebraska and Mis- 
souri. The Supreme Court finally decided that when the Missouri 
develops a cut-off, the boundary line does not shift with the river, 
but remains where it was. Again, many boundaries have been 
defined as following the "main channels" of streams. Where there 
are several channels, which is the case in many rivers, the question 
may arise as to which one is the main channel. Furthermore, the 
main channel at one time may be a subordinate channel at another 
time. These conditions have led to disputes over the ownership 
of islands in different rivers. A curious situation exists where the 
Menominee River forms the boundary line between Wisconsin and 
Michigan. This line was fixed along the main channel, and later 
the question of the ownership of certain islands was found to be 
involved. Congress provided that Michigan should own the islands 
above Quinnesec Falls, and Wisconsin those below. But in places 
below the falls, the main channel, which is defined as the boundary, 
lies to the west of the islands. In other words, Wisconsin owns 
islands in Michigan. 

The objections to rivers as boundaries are most serious where 
they form international boundaries. Thus the shifting of the Rio 
Grande makes it an unsatisfactory boundary between the United 
States and Mexico. In addition, so much water was diverted from 
the Rio Grande for irrigation in southern Colorado and New Mexico 
that there was little water for Mexican farmers below El Paso. 
Mexico protested to the United States, and finally it was arranged 
that the United States should construct a great reservoir on the Rio 
Grande north of El Paso, to regulate and conserve the water of 
the river, and that Mexico should receive a certain fixed amount 
of water from this reservoir each year. It may be noted in passing 
that many of the parallels and meridians which separate counties 
and states really were fixed by river features. Thus, the southern 
part of the western boundary of Missouri is a line running due south 
from the mouth of the Kansas River, while the east and west line 



372 



ELEMENTS OF GEOGRAPHY 



which forms the northern boundary of the state was fixed by the 
falls of the Des Moines River. 

Most flood-plains are of great fertility, but many are too wet 
to be cultivated without drainage. About one-sixth of Arkansas, 
for example, is swampy, but most of its swamp area is rich alluvial 
land. When reclaimed, the wet lands of the United States will 
constitute one of the greatest resources of the nation (p. 459). 

Deltas and their relations to man. Where a stream flows 
into the sea, or into a lake } its current is checked promptly, and 




Fig. 257. A delta in a lake. The village is Silva Plana, in the Engadine, 
Switzerland. (From photograph by Robin.) 



soon stopped entirely. Its load therefore is dropped, and if not 
washed away by waves and currents, makes a delta (Fig. 257). That 
part of a delta above the surface of the water in which it is built 
is like a flat alluvial fan. Waves and currents may prevent the 
building of a delta, but otherwise all sediment-bearing streams 
make deltas where they enter lakes or seas. Deltas may be built 
where one stream flows into another, especially where a swift stream 
with much sediment joins a slow one. 

Much land has been made by the growth of deltas. Thus the 
Colorado River has built a great delta many square miles in area 
at the head of the Gulf of California (Fig. 258). The delta has 
been built across the gulf near its former upper end, shutting off 
the head. In the arid climate of the region, this shut-off head be- 
came a nearly dry basin, the lowest part of which is about 300 feet 
below sea-level. The soil being good, water alone was needed 
to give this area great agricultural value, and the results that 
have followed the irrigation of parts of it justify its new name, the 



MODIFICATION OF LAND SURFACES 



373 



"Imperial Valley." Figs, dates, and other tropical products grow 
here luxuriantly. 

In 1906, this low land experienced much trouble. The Colorado 
River broke out of its banks, and pouring into the basin, made a 




Fig. 258. Map showing the delta of the Colorado River and its surroundings. 



great lake, called the Salton Sea (or Sink; Fig. 258). The lake 
spread over farming lands, villages, and railroads, and vast sums of 
money were expended in turning the water back into its old course. 

While rivers have made much delta land, it is to be remembered 
that the material of which they are composed has been removed 
from vastly larger areas, and that much of it was rich soil. It is 



374 



ELEMENTS OF GEOGRAPHY 



probable that the loss to man through the removal of such material 
is far greater than the gain resulting from its deposition. 

The deltas of the Mississippi (Fig. 259), the Nile (Fig. 260), 
and the Hwang-ho (Fig. 261) rivers are among the large and well- 
known ones. The delta of the Ganges and Brahmaputra has an- 
area (above water) of some 50,000 square miles (nearly as large as 
Illinois). 

When a delta is built in the head of a bay, the outline of the bay 
determines the shape of the delta. In other situations the normal 



V . wrt^ 




■*$ ^> 






Fig. 259. The lower part of the delta of the Mississippi River. 



form of a delta is roughly semi-circular, though there is in many 
cases a fringe of delta fingers, which together have some resemblance 
to the Greek letter (A) which gave these terminal deposits of 
streams their name. The surfaces of most deltas are nearly flat, 
and the streams which cross them often give off branches, called 
distributaries, which flow independently to the edge of the delta, 
and are subject to frequent changes. These changes sometimes 
affect commerce in a vital way (p. 519). The distributaries of the 
Mississippi offered the English in the War of 181 2, and the Federals 
in 1862, several possible avenues of approach to the vicinity of 
New Orleans. The necessity of watching these different lines scat- 
tered the men and the resources, and weakened the resistance of 



MODIFICATION OF LAND SURFACES 



375 




Fig. 260. Delta of the Nile 
River. The dotted area is 
desert. 



the defenders of the city. By cutting the levees and flooding the 
lower land, General Jackson was able to increase greatly the diffi- 
culties of the English. 

Most delta land away from natural levees is low and wet, neces- 
sitating diking and drainage before agriculture can be undertaken. 
The soil of great deltas is deep (What 
determines its thickness?) ; in most cases 
rich in the mineral elements of plant 
food, for the varied rocks of the entire 
drainage basin have contributed to it; 
and fine, for most of the coarse material 
is dropped farther up river. On the 
other hand, the material of many small 
deltas built by swift streams in moun- 
tain lakes, is coarse. Some deltas, like 
that of the Hwang-ho, support dense 
populations. Delta lands are, however, 

subject to disastrous floods. It is estimated that the flood of the 
Hwang-ho River in September, 1887, drowned more than a million 
people and caused the death of many more by disease and famine 
afterward. Many villages were destroyed, and hundreds more were 
submerged temporarily. Pre- 
vious to 1853, this river had 
flowed for many years into the 
Yellow Sea south of the Shan- 
tung promontory (Fig. 261). 
In that year, it shifted its 
course in flood time, forming a 
new channel leading northeast 
into the Gulf of Pechili, 300 
miles north of its former mouth. 
Comparable changes at earlier 
times, running as far back as 
2293 B. C, are recorded in the 
annals of Chinese history. 

Lakes are characteristic fea- 
tures of many large deltas. Some represent former sections of the 
shifting streams, and some (Fig. 259) are portions of the sea or lake 
in which the delta is built, portions that were surrounded by the 
growing deposits or shut in between them and the former shore-line. 





/ y>yJkw M52* 


/ yg^.6 Ho SA"f = 






''■'V^'\ "^^f^^Old Mouth 



Fig. 261. Delta of the Hwang-ho. 



376 



ELEMENTS OF GEOGRAPHY 



Delta cities have peculiar municipal problems, as illustrated 
by New Orleans. For a long time, inundations were of almost 
yearly occurrence. In 1849, for example, 220 inhabited squares 
were flooded and 12,000 people were driven from their homes. Street 
improvement was difficult; there were no paving stones save those 
brought as ballast in ships. As late as 1835, only two streets were 
paved for any considerable distance. On the other streets, car- 




Fig. 262. Terrace of the Columbia River. (Willis.) 



riages in wet weather sank to the axle in mire. The question of a 
domestic water supply was an early and pressing one. The practice 
of building cisterns to catch the rain-water became general, and the 
supply still is obtained partly from rains. The city cannot empty 
its sewage into the Mississippi, for the banks of the river are above 
the houses. Under these conditions, the city was for years a very 
unhealthful place. 

Alluvial terraces. When a river which has an alluvial flat 
is rejuvenated (p. 360), the stream sinks its channel below the level 
of the flat. The remnants of the old flood-plain are then alluvial- 
terraces. Such terraces are also formed in other ways. Thus if 
a stream is supplied for a time with an excess of load, it aggrades 
(builds up) its valley. If, later, the excess of sediment ceases, the 
stream sets to work to remove that which was temporarily laid aside 
in its flood-plain (Fig. 262). 

The material of many alluvia 1 terraces is gravelly or sandy, 



MODIFICATION OF LAND SURFACES 377 

and their soils vary greatly in value. Many towns and cities have 
had their position determined by alluvial terraces. (What advan- 
tages would such locations be likely to have over sites on flood-plains? 
Sites on the edges of valley bluffs?) The leading towns of the Platte 
Valley in Nebraska are situated on terraces near the mouths of 
tributary valleys. (Of what significance is the last fact?) In the 
middle Illinois Valley, every town is on a terrace, and every terrace 
has a town. Terrace sites were chosen for most of the first settle- 
ments of the Connecticut Valley, such as Hartford, Weathersfield, 
and Windsor. 

Summary. From the physiographic standpoint, the mission of 
running water is to wear the land to base-level. The material it 
carries toward and to the sea is prepared for transportation largely by 
the agents of weathering, and in subordinate amount is worn from the 
solid rocks by the streams themselves. The irregular wearing down 
of the land produces most of the familiar relief features of the surface. 
Their characteristics are determined by several factors, especially 
by the character and position of the rocks from which they were 
carved, and the stage of development which they have reached. On 
its way to the sea, the waste of the land is often laid aside by over- 
loaded streams, forming topographic features subject to later 
destruction by eroding waters or by other agencies. All phases of 
river work affect human interests vitally. Much can be done by 
regulating and controlling streams to increase their usefulness and 
prevent their doing damage. 

QUESTIONS 

1. (1) Under what conditions must a valley be deep to have a stream? (2) 
Under what circumstances may even shallow valleys have permanent streams? 
(3) In what parts of the United States would you expect to find examples of each 
type of valley? 

2. What are all the conditions which may help to make the flow of streams 
(1) regular, and (2) irregular? 

3. Why do streams carry more and coarser material during floods than at 
other times? 

4. Is the bed of the upper St. Lawrence River being eroded much or little? 
Why? 

5. (1) Why is the rate of erosion in the Colorado Basin so rapid (Fig. 210), 
especially in view of the fact that a large part of it is in an arid region? (2) Why 
is the rate in the basin of the Red River of the North relatively so slow (Fig. 210)? 

6. Enumerate the various factors upon which the length of life of a water- 
fall will depend. 



378 



ELEMENTS OF GEOGRAPHY 



7. Why are steep slopes characteristic of arid climates? 

8. In what ways may a valley come to have a cross-section like that shown 
in Fig. 263? 

9. What is the age, in terms of erosion, of the area shown in Fig. 143? 

10. (1) What is the age, in terms 

of erosion, of the area shown in pro- 
file in Fig. 264? The evidence? (2) 
To what may the differences in the 
size of the valleys be due? (3) What 
changes will occur in the topography 
of the region in the future? 
11. (1) Interpret the contrasted drainage shown by Figs. 265 and 266. (2) 
In what stage of erosion is the area shown by Fig. 265? (3) Does Fig. 266 indi- 
cate the stage of erosion which that area has reached? Why? 




Fig. 263. Cross-section of a valley. 



Fig. 264. Profile of an area north of Chicago, near Lake Michigan. Length 
of section, 4 miles. 

12. (1) What topographic features are shown in Fig. 267? (2) Compare 
and contrast the northern and southern parts of the area as to (a) the climate, 
(b) the character of the rocks, and (c) the work of the streams. 





Figs. 265, 266. Drainage maps of contrasted areas of equal size. 



13. In general, what stream-built features are (1) most and (2) least endur- 
ing? Why? 

14. Enumerate all the important ways in which (1) stream erosion and (2) 
stream deposition affect human interests. 



MODIFICATION OF LAND SURFACES 

REFERENCES 



379 



Darton: Examples of Stream-robbing in the Catskill Mountains, in Bull. 
Geol. Soc. of Am., Vol. VII, pp. 505-507. 

Davis: The Seine, the Meuse, and the Moselle, in Nat. Geog. Mag., Vol. VII, 
pp. 189-202, 228-238. 

Davis: The Rivers and Valleys of Pennsylvania, in Nat. Geog. Mag., Vol. I, 
pp. 183-253. 

Davis : River Terraces in New Eng- 
land, in Bull. Harvard Mus. of Comp. 
Zool., Vol. XXXVIII, pp. 281-346. 

Davis: The Physical Geography 
of Southern New England, in Physi- 
ography of the United States, pp. 
269-304. (New York, 1895.) 

Davis and Wood: The Geog- 
raphic Development of Northern New 
Jersey, in Proc. Bost. Soc. Nat. Hist., 
Vol. XXIV, pp. 365-423. 

Dodge: The Geographical De- 
velopment of Alluvial River Terraces, 
in Proc. Bost. Soc. Nat. Hist., Vol. 
XXVI, pp. 257-273. 

Dutton: Tertiary History of the 
Grand Canyon District; Mono. II, U. 
S. Geol. Surv. 

Gannett : Profiles of Rivers in the 
United States; Water Supply and Irri- 
gation Paper No. 44, U. S. Geol. Surv. 

Gilbert: Land Sculpture, in Geol- 
ogy of the Henry Mountains, pp. 
99-150; U. S. Geog. and Geol. Surv., 
Rocky Mtn. Region. (Washington, 

1877O 

Gilbert: Niagara Falls and 
Their History, in Physiography of the 
United States, pp. 203-236. (New 
York, 1895.) 

Hayes: The Southern Appala- 
chians, in Physiography of the United States, pp. 305-336. (New York, 1895.) 

Johnson, L. C. : The Nila Crevasse, in Bull. Geol. Soc. of Am., Vol. II, pp. 20-25. 

Powell: Exploration of the Colorado River of the West and Its Tributaries. 
(Washington, 1875.) 

Russell: Rivers of North America. (New York, 1898.) 

Salisbury: The Physical Geography of New Jersey; N. J. Geol. Surv., Vol. 

IV, pp. 65-154. 

Willis: The Northern Appalachians, in Physiography of the United States, 
pp. 169-202. (New York, 1895.) 

See also general texts mentioned on p. 312. 




Fig. 267. 



380 ELEMENTS OF GEOGRAPHY 

The Work of Ice 

Snow is perhaps the most common form of ice, but ice on ponds, 
lakes, and rivers is familiar to all who live where the winters are 
cold. In middle latitudes the water in the soil and rocks freezes 
in winter, often to a depth of several feet. In some parts of the 
world, too, there are glaciers. In most of its forms ice has some 
effect on the surface of the land. 

Ice on lakes and rivers. Most lakes and rivers in middle lati- 
tudes are frozen over for several months each year. This is in some 
cases a great disadvantage from the standpoint of commerce. The 
upper Mississippi River is closed to navigation for more than four 
months of the year. The Illinois and Michigan Canal, connect- 
ing Lake Michigan with the Illinois River, was open to navi- 
gation, on the average, only 237 days each year between 1848 and 
1902. The open season on the upper Great Lakes lasts for only 
about seven months. The St. Lawrence River is closed by ice for 
five months each year, and is difficult to enter during another month. 
Hudson Bay and its tributary rivers are closed even longer. It 
was a great disadvantage to the French colonies of interior Canada 
that they were shut off completely from the mother country for 
nearly half the year, and it is a serious disadvantage to Canada to- 
day that her two main gateways from the Atlantic Ocean are closed 
so much of the time. The inland waterways of England and France 
are open throughout normal years; those of Germany and central 
Russia are closed more often, and for longer times as one goes east; 
and those of northern Russia are closed for five or six months. (Why 
these differences? Why are the waterways of western Europe so 
in contrast with those of North America in corresponding latitudes?) 

In some cases, the ice of rivers and lakes serves a good purpose. 
Fishing villages formerly were established on the ice in such places 
as Saginaw Bay, and are still common in the gulfs of Bothnia and 
Finland. When frozen over, many northern rivers serve as road- 
ways for local business. Under the influence of Lake Champlain 
and the Richelieu River, the people of western Vermont for years 
had much closer relations with Canada than with the rest of New 
England. After midwinter, when Lake Champlain had become a 
plain of ice, long trains of sleighs went to Montreal with loads of 
produce to exchange for merchandise or money. The Alaskan 
rivers and those of Siberia also are much used for travel when cov- 



MODIFICATION OF LAND SURFACES 381 

ered with ice. The harvesting and packing of ice for sale during 
the ensuing summer is an important industry on many lakes and 
rivers. in northern United States. 

When river ice breaks up in the spring, stones and bowlders to 
which it was frozen in the banks may be floated down-stream for 
miles. Again, masses of river ice may gather in vast "jams" behind 
dams or bridges, and the latter may be swept away. The jams them- 
selves form an obstruction, holding back the water and causing 
floods above. When a jam breaks, the water above may sweep down 
the valley with destructive violence. 

Ice on the sea. In high latitudes ice forms on the sea where 
the water is shallow, and in polar regions it becomes several feet 
deep, even on the open sea. Sea-ice is broken up in the summer, 
and the floating pieces are called floe-i ce. When the floes are crowded 
together, they make ice-packs, some of which are hundreds of miles 
across. Ice-packs are one of the obstacles to polar navigation, and 
make most of the north coast of Russia and Siberia useless even in 
summer. 

The closure of ocean harbors and of seas connected with the 
ocean, like the closure of inland waters, is a matter of great im- 
portance to commerce. The North Sea has a tremendous advantage 
over the Baltic Sea in this regard. The shores of the latter are ham- 
pered by ice each winter, while those of the former are edged with 
ice only during the most severe weather. The key to Russian expan- 
sion since the days of Peter the Great has been the attempt to secure 
ice-free harbors. 

Ice beneath the surface. The wedge-work of ice in the cracks 
of rock has been mentioned (p. 261). Since a freezing temperature 
occurs during some part of the year over more than half the earth, 
the total effect of the freezing of water in the pores and crevices of 
rock must be great in long periods of time. Water freezing in the 
soil sometimes "heaves" (displaces) walls, if they do not go below 
the depth of freezing, and it sometimes "works up" stones and 
bowlders through the soil. Frozen water in the soil has a protective 
effect also. It makes the soil solid for the time being, and so 
retards or prevents erosion by wind and water. On the other hand, 
if heavy rains fall, or if much snow melts quickly while the ground 
is frozen, floods are increased. 

In high latitudes the ground always is frozen below a depth 
of a few feet (p. 221). 



382 



ELEMENTS OF GEOGRAPHY 



EXISTING GLACIERS 

General 
Conditions for glaciers. Where the temperature is so low 
that snow endures from year to year over any considerable area, 
the snow constitutes a snow-field (Fig. 268). Snow-fields occur in 
mountains in nearly all latitudes, and in polar regions even down to 
sea-level. Where snow accumulates to great depths and lies long on 
the surface, it changes to compact ice, and becomes an ice-field. The 
beginning of this change is distinct in the last banks of snow in the 
spring. Such banks are made up of coarse granules of ice, sometimes 




Fig. 268. Snow-fields in Alaska. 
Canadian Boundary Commission.) 



Russell Fiord at right of view. (Brabazon, 



as large as peas. The change from flakes of snow to granules of ice 
is due, in part, to the melting of the snow and the re-freezing of the 
water. If there is much snow, it-, is compressed by its own weight, 
and after being compacted in this way, the freezing of the sinking 
water binds the granules together. When the amount of ice made 
from snow becomes great enough, it moves out slowly from the 
place where it was formed to lower and warmer places. When it 
begins to move, it becomes a glacier. 

Functions of glaciers. (1) One mission of glaciers is to return 
to lower and warmer levels moisture which otherwise would be 
imprisoned indefinitely as snow and ice. (2) Like rivers, glaciers 
wear the land and move the resulting waste toward the sea. (3) 
Long after glaciers have melted away, some of their effects on the 



MODIFICATION OF LAND SURFACES 383 

conditions of life remain, because of the changes they made in topog- 
raphy, soil, and drainage. Thus past glaciation is a primary factor 
in the geography of northern United States and northern Europe. 
(4) Glaciers tend to maintain a relatively uniform volume in the 
streams which flow from them, and in various mountain regions 
such streams afford great amounts of power. The "white coal" 
of Switzerland is probably the greatest natural resource of that 
country. Electricity developed by water power runs railways, 
lights cities and villages, supplies power in many mines, and is avail- 
able to more than two-thirds of the people for various uses. The 
electric motor is being substituted for manual labor in many of 
the household industries of Switzerland, and by electricity "grain 
is being threshed, milk is being churned to butter, water is being 
pumped, food for the cattle is being prepared, and the farmer is 
being relieved of his most arduous labor." 

Types of glaciers. Glaciers have various forms, depending 
on the amount of ice and on the shape of the surface beneath and 
around them. If the snow-field which gives rise to a glacier is 
at the upper end of a mountain valley, the ice moves down the valley 
as a valley glacier (Fig. 269). In high latitudes, snow-fields and 
ice-fields may lie on plains or plateaus. When the ice in such situ- 
ations begins to spread, it moves in all directions from its center. 
Such glaciers are ice-caps or ice-sheets. Very large ice-caps some- 
times are called continental glaciers. The main ice-caps of Antarctica 
and Greenland (Fig. 270) are large, but small ones are found on 
various promontories along the coast of Greenland, on Iceland, and 
on some Arctic islands. Glaciers occur also at the bases of some 
mountains, being formed by the union of the spreading ends of 
valley glaciers. Such glaciers are piedmont glaciers (Fig. 272). Of 
these types, valley glaciers are most common and most familiar, but 
the large ice-caps contain much more ice. 

Valley Glaciers 
Distribution. The chief regions of valley glaciers are the 
high mountains of Eurasia, such as the Alps, Caucasus, and Hima- 
layas; the southern Andes; and the higher mountains of northwest- 
ern United States and western Canada. In Alaska, lofty mountains 
near the coast compel the abundant precipitation of moisture brought 
by westerly winds from the Pacific Ocean. The heavy snowfall on 
the upper slopes feeds many glaciers, some of which reach the sea. 



384 



ELEMENTS OF GEOGRAPHY 



The glaciers of Switzerland are known best and help to attract thousands of 
tourists to that country each year. In 1910, Congress created Glacier National Park 
on the Continental Divide in northwestern Montana (Fig. 359). It is about sixty 
miles in length and contains more than sixty glaciers. The glacier-fed streams 
flowing from the park will have great importance in connection with irrigation 




Fig. 269. A valley glacier in the Cascade Mountains, Washington. 
U. S. Geol. Surv.) 



(Willis, 



and the development of water power. The water flowing from some of these 
glaciers finally reaches Hudson Bay; that from others goes to the Gulf of Mexico; 
and still others are tributary to the Pacific. This may become one of the best 
known and most visited of our National Parks, for the mountains and glaciers 
offer the chance for mountaineering of real Alpine character, the streams abound 
in trout, and the mountains still shelter enough game animals to' become an im- 
portant game refuge. The park contains one of the most beautiful portions 
of the Rocky Mountains lying within the United States. 



MODIFICATION OF LAND SURFACES 385 

Size. There are nearly 2,000 glaciers in the Alps, only one 
of which has a length of ten miles. Less than 40 have a length 
of five miles, while the great majority are less than one mile long. 
Only a few are so much as a mile wide, and none are more than a 
few hundred feet thick. Larger glaciers occur in the Caucasus 
Mountains and in Alaska. Seward Glacier in Alaska is more than 
50 miles long, and three miles wide at the narrowest place. The 
glaciers of western United States south of Alaska are not so large 
as the larger glaciers of the Alps. 

Movement. The ice of a glacier is wasting continually, both 
by melting and evaporation. In spite of this, many glaciers remain 
about the same size year after year. This is because the loss by 
melting is replaced by advance from the snow-fields, from which the 
ice creeps down the valleys until it reaches a place so warm that the 
melting at the end balances the forward motion. 

Most glaciers move very slowly. Of those whose rate of ad- 
vance has been measured, few move more than two feet a day, and 
very few as much as seven. The rate of movement depends chiefly 
on (1) the thickness of the moving ice, (2) the slope of the surface 
over which it moves, (3) the slope of the upper surface of the ice, 
and (4) the topography of its bed. N (What combination of condi- 
tions would favor most rapid movement?) The exact nature of 
glacier movement is a disputed question. It was thought formerly 
that glaciers flowed somewhat as stiff liquids do, but it is very doubt- 
ful if the motion is really flowage. 

Ice-Caps 

As already stated, ice-caps may lie on plains or plateaus, and 
may be large or small. 

The area of Greenland has been estimated variously at from 
400,000 to 600,000 square miles, and all but its borders is buried 
beneath one vast field of ice and snow (Fig. 270). Except on a nar- 
row border of a mile or so at the edge of the ice-sheet, not even a 
bowlder or a pebble relieves the great expanse of white. 

The thickness of the Greenland ice is not known, but, where 
thickest, it is probably thousands of feet. Near its margin the 
ice is much crevassed, but the interior is comparatively smooth so 
far as known. The ice of this great field is creeping slowly outward. 
The rate of movement never has been measured, and is probably 
not the same at all points, but it has been estimated not to exceed a 



3 86 



ELEMENTS OF GEOGRAPHY 



foot a week. This ice-cap is, in one sense, more of a desert than 
the Sahara, since it is inhabited even less than the latter. 

Where the edge of the Greenland ice-cap lies a few miles back from 
the coast, the rock plateau outside it has numerous valleys leading 
down to the sea. Where the edge of the ice-cap reaches the heads of 
these valleys, ice moves down them, making valley glaciers. Many of 

the latter reach the sea, where 
their ends are broken off and 
float away as icebergs. This is 
the source of most of the bergs 
(Fig. 271) seen from steamers 
which cross the North Atlantic. 
Some are so large that they float 
far to the south before they are 
melted. Since they are some- 
times surrounded by fog, they 
may be a menace to navigation. 
The Antarctic snow-and-ice- 
cap is far more extensive than 
that of Greenland, but its area 
is not so well known. It is 
probably several million square 
miles in extent, and the thick- 
ness of its ice probably exceeds 
that of Greenland. The ice 
descends to the sea at many 
points (p. 218), and huge blocks 
of it become icebergs. 




Fig. 270. Map of Greenland ice-sheet. 



Piedmont Glaciers 
A number of alpine glaciers 
come down adjacent valleys in 
the St. Elias range of Alaska, and spread out on a low plain at its 
base. So much do their ends spread that they unite to form a 
single body of ice, 70 miles long and 20 to 25 miles wide, called the 
Malaspina Glacier (Fig. 272). Its area is greater than that of Dela- 
ware. Its central portion is free from debris, but is interrupted by 
thousands of deep, wide cracks. A belt along the margin of the 
glacier five miles or less in width is covered by rocky and earthy 
debris, and parts of it are clothed with vegetation. The under- 



MODIFICATION OF LAND SURFACES 



387 



growth is here so thick that travelers have to cut paths, and on the 
edge of the ice there are trees three feet in diameter. Another large 
but unexplored glacier of the same type lies a few miles west of the 
Malaspina, and others occur 
about North Greenland. 

ANCIENT GLACIERS 

There have been times when 
glaciers were much more ex- 
tensive than now, for various 
features produced only by gla- 
ciation (pp. 391-405) are found 
in many places that are now free from ice 
periods is known as the Glacial Period 




Fig. 271. An iceberg. 



The latest of these 
In this country, glaciers 
existed even in the mountains of New Mexico, Arizona, and Nevada. 
The amount of ice in the glaciers of Utah or Colorado was then 
far greater than all that now exists in the United States south of 
Alaska. At the same time, a great area east of the Cordilleran 




Fig. 272. The Malaspina Glacier, and numerous valley glaciers. (Model by 
Martin; copyright by University of Wisconsin.) 



3 88 



ELEMENTS OF GEOGRAPHY 



mountain system, some 4,000,000 square miles in extent (Fig. 273), 
and lying partly in Canada and partly in the United States, was 
covered with an ice-sheet. 




Fig. 273. Sketch-map showing the area in North America covered by ice at 
the stage of maximum glaciation. (Chamberlin.) 



The ice-sheet of North America originated in two principal cen- 
ters, one on either side of Hudson Bay. The beginning of each was 
doubtless a great snow-field. At first these snow-and-ice fields grew 
by the addition of snow, and later also by the spread of the ice to 



MODIFICATION OF LAND SURFACES 389 

which the snow gave rise. The two ice-sheets finally became one 
by growing together. This great continental glacier did not origi- 
nate in mountains, but on high plains, where the topography had 
been shaped mainly by river erosion. 

When largest, this ice-sheet covered all New England, northern 
New Jersey and Pennsylvania, and much of Ohio and Indiana. 
Its edge crossed the Ohio River where Cincinnati stands, and ad- 
vanced a few miles into Kentucky. Farther west it reached almost 
to the southern end of Illinois. Its edge crossed the Mississippi 
near St. Louis, and followed, in a general way, the course of the 
Missouri River to western Montana. Most of the continent north 
of this line was covered with snow and ice, but there was an area 
of 8,000 to 10,000 square miles, mainly in southwestern Wisconsin, 
over which the ice did not spread. This is known as the driftless 
area, because there are no ice deposits in it. In the Cordilleran 
mountains there was also a great body of ice which remained some- 
what distinct from that which spread from the other centers. 

There was extensive glaciation in Europe at about the same time 
as in North America. The glaciers of the Alps were then many 
times as large as those of to-day. On the south they extended 
quite beyond the mountain valleys, and spread out on the plains 
of northern Italy, where they left their deposits. Similar condi- 
tions existed in the other mountains of Europe where glaciers now 
exist, and in some where glaciers are not now present. There was 
also a large ice-sheet in Europe (Fig. 274), but its area was only 
about half that of the ice-sheet of North America. The principal 
center from which the ice spread was the mountains of Scandinavia. 

Great ice-sheets are not known to 'have developed in other con- 
tinents during the Glacial Period, but their valley glaciers were 
very large. 

The history of the continental glaciers was complex, both in 
Europe and in North America. After the growth of the first great 
North American ice-sheet, it shrank to small size, or disappeared 
altogether. Then followed a relatively warm period, when plants 
and animals lived in the region abandoned by the ice. Another 
continental ice-sheet then developed, spreading over the region from 
which the first had melted, and extending still farther south. As 
it advanced, the second ice-sheet in places buried the soil which had 
formed on the drift left by the ice of the first epoch. Such soils, 
here and there with the remains of plants which grew in them, are 



39° 



ELEMENTS OF GEOGRAPHY 



one means by which it is known that there was more than one ice- 
sheet. A third, fourth, and fifth ice-sheet, each somewhat smaller 
than its predecessor, developed and disappeared. In other words, 
there were several epochs when ice-sheets were extensive, separated 
by epochs when they were much smaller, or when they had disap- 
peared altogether. The ice-sheets of Europe had a similar history. 

Cause of the glacial epochs. The development of the great 
ice-sheets was due to a change in climate, and especially to a reduc- 




Fig. 274. Sketch-map showing the area of Europe covered by the continental 
lacier at the time of its maximum development. (James Geikie.) 



tion of temperature. The cause of the cold is not known, though 
many explanations have been suggested. One is that the northern 
lands were raised to great heights. Another is based on changes 
in the shape of the earth's orbit, and on changes in the direction of 
the earth's axis. The hypothesis which seems most acceptable is 
that the change of climate was due to a change in the constitution 
of the atmosphere. An increase in the amounts of carbon dioxide 
and water vapor would make the climate warmer, while a decrease 



MODIFICATION OF LAND SURFACES 



39i 



in these things would make it colder. Good reasons have been 
suggested for variations in the amounts of these substances in the 
air, and also for the heavy precipitation in the regions where the 




Fig. 275. Glaciated surface of limestone. The view shows also the relation 
of drift to the bed-rock beneath. Kelleys Island, Ohio. (Stauffer.) 

ice-sheets existed. Heavy snowfall is as necessary as low tempera- 
ture for extensive glaciation. 



CHANGES DUE TO GLACIAL EROSION 

How glaciers erode. Clean ice, moving over smooth, solid 
rock, would erode little, but ice carrying pieces of rock in its under 
layers wears the surface, even when the latter is smooth and solid. 
Like wind and water, therefore, ice erodes by means of the rock tools 
which it carries. The bottom of a glacier secures tools in various 
ways. (1) As a snow-field accumulates, it may lie upon an uneven 



39 2 



ELEMENTS OF GEOGKAPHY 



surface covered with loose pieces of rock. These are covered and 
enclosed by the snow, and when the latter becomes ice and begins 
to move, they are carried along with it. A glacier, therefore, has 
tools from the outset. (2) As a glacier creeps out over surfaces 
covered with soil, it becomes united to the ice in the soil, in part 
by the freezing of descending water. Further movement of the 
glacier causes some of the soil to be carried forward. 

The loose material removed by a glacier from the surface 
is used to wear the bed-rock farther on. Each kind of tool does 




Fig. 276. Glacial trough in San Juan Mountains, Colorado. 



its appropriate work. Fine, earthy material in the bottom of the 
ice polishes the rock below, while sand and small pebbles make 
scratches {stria) upon it. Grooves are made by bowlders held in 
the bottom of the ice and urged along under great pressure. Mean- 
while the tools are themselves polished, scratched, and worn smaller 
and smaller. The finest products of the grinding have been called 
rock flour. Polished and striated bed-rock surfaces (Fig. 275) are 
among the clearest marks of the former existence of glaciers in many 
places now free from ice. 

Changes in valleys. Mountain valleys through which glaciers 
pass are widened and deepened, and their walls made smoother 
(Figs. 276 and 277). In many cases the heads of glaciated valleys are 
big, blunt, and steep-sided. Most of the lakes which add so much to 
mountain scenery are (1) in rock basins gouged out of valley floors 
by glaciers (Fig. 277), or (2) behind dams formed by the deposits 
of the ice (Fig. 278). Tributary valleys commonly join their main 
valleys at the level of the latter, but the bottoms of many valleys 



MODIFICATION OF LAND SURFACES 



393 



that were deepened and widened by former glaciers are much (in 
some cases 500 to 1 ,000 feet) lower than the lower ends of their tribu- 
taries. In such cases streams descend in rapids or falls from the 
tributary hanging valleys (Fig. 279). Much water power is afforded 
by such rapids and falls in the western mountains. 

The ancient ice-sheet overrode hills and divides as well as valleys. 
In many cases the ice deepened the valleys more than it lowered 



'"-v 



'"-\ 



"Y 




Fig. 277. A valley in the Needle Mountains, Colorado, cleared of all earth 
and loose rock by a glacier which once passed through it. The moving ice also 
smoothed all the projecting points of rock. 



the hills, and where this was true, it increased the relief, even though 
it reduced the roughness of the surface. 

Elevations reduced and changed in shape. Hills overridden 
by ice-sheets are worn down and smoothed off, and the wear is 
greatest on the side of the hill against which the ice moves (Fig. 
280). Many small elevations were worn away entirely by the 
continental glaciers. 

Ice-shaped coasts. Glaciers which descend into the sea through 
bays tend to gouge out the bay-bottoms, and to wear back the bay- 
heads. If such glaciers melt away, the sea enters to form long, 



394 



ELEMENTS OF GEOGRAPHY 



narrow, steep-walled re-entrants, called fiords. Norway (Fig. 281), 
Scotland, Maine, and Alaska have fiord coasts, though all of them 

owe their characteris- 
tics in part to sinking. 
Many islands front 
these coasts, most of 
them representing ele- 
vations of the old land 
whose surroundings 
have been drowned. 

GLACIAL DEPOSITS 



General character- 
istics. Most of the 
material transported 
by a glacier is carried 
in its lower part; but 
some is carried in the 
ice above its bottom, 
and some on top of the ice. All of it is left, finally, on the surface 
of the land. The materials deposited by glaciers, called glacial drift 
or till, range from finest earth to huge bowlders many feet in diameter 




Fig. 278. Convict Lake, east base of Sierra 
Nevada Mountains, California. The lake is formed 
by a morainic dam. (Fairbanks ) 




Fig. 279. Hanging valley on south side of Nunatak Fiord, Alaska. (Tarr, 
U. S. Geol. Surv.) 



(Figs. 282 and 283). They are not stratified, and are so deposited 
in many places as to form distinctive topographic features. Much 
of the drift deposited by the continental glaciers is a thorough 



MODIFICATION OF LAND SURFACES 



395 



mixture of many kinds of material, for it was derived from a vast area 
within which practically all kinds of rocks occur. (Compare these 
features with those of 
stream deposits.) 

Leading types. 
When the end of a 
valley glacier or the 
edge of an ice-cap stays 
in the same place for a 
long time, a thick body 
of drift is lodged be- 
neath it, for drift is 
brought to this position 
continually by the on- 
coming ice, and left 
there. Such a deposit 
is a terminal moraine 
(Fig. 284). All the other drift deposited by an ice-sheet is ground 
moraine. After a glacier melts, the area of ground moraine is not as 
great as the glaciated area, for glaciers do not carry debris in all parts 
of their bottoms. In general, the drift is thickest and covers the 




Fig. 280. A hill smoothed by the glacier ice 
which overrode it. Shore of North Greenland. 
(From photograph by Chamberlin.) 




Fig. 281. The Sogne Fiord, coast of Norway. (Robin.) 



largest proportion of the surface near the margins of a glaciated area, 
and is thinnest and least continuous in the region from which the ice 
spread (Why?). For this reason, there are large areas of bare rock 
and of thin, bowlder-strewn soil on the uplands of eastern and north- 
eastern Canada. Together with a bleak climate, these conditions 
render large areas unfit for agriculture. Much of the material 
removed by the ice from Canada was deposited in the United States. 



396 



ELEMENTS OF GEOGRAPHY 




Fig. 282. Section of unstratified drift near 
Henry, Illinois. (Crane.) 



The ice of a valley glacier moves toward either side of the valley, 
as well as down-valley, and as it spreads sidewise from the center, 
it shifts debris from the axis of the valley to the edge of the ice on 

either side. The lateral 
moraines left along the 
sides of a valley after 
the ice is gone (Fig. 
285) are composed 
chiefly of this material, 
but partly also of the 
debris that composed 
the lateral moraines 
which were on the gla- 
cier (Fig. 286). The 
lateral moraines left in 
valleys are hundreds of 
feet high in many cases, 
and more than a thou- 
sand feet high in some. 
Surface features. Because glaciers distribute their drift very 
unevenly, large areas once covered by ice are marked by hillocks, 

mounds, and ridges, 
and by basin-like or 
trough-like depres- 
sions. These features 
are most pronounced 
in terminal moraines, 
the surfaces of which 
may be distinctly 
rough and hummocky 
(Fig. 287). In typical 
ground moraines hills 
are lower, basins shal- 
lower, and slopes 
gentler. 

In the Lake States, 

the rougher parts of 

the terminal moraines commonly are used for woodlots and pastures 

(p. 275), for the surface is too uneven and the soil too coarse and 

stony to be cultivated successfully, in competition with the neigh- 




Fig. 283. A glacial bowlder near Hibbing, 
Minnesota. (Van Cleef.) 



MODIFICATION OF LAND SURFACES 



397 



boring prairies. Many of the hollows in the surface of the drift 
contain lakes (p. 399), ponds, and marshes (p. 458). It is estimated 
that there are 4^ million acres of marsh land in Minnesota, nearly 




Fig. 284. A glacier in the Cascade Mountains, Washington. Shows spreading 
end of glacier, crevasses in ice, and terminal moraine. (Willis, U. S. Geol. Surv.) 



as much in Michigan, and 2^2 million in Wisconsin. The total 
swamp area for the three states is larger than the combined area 
of Massachusetts, Connecticut, Rhode Island, and Delaware. Nearly 
all this swamp land is the result of glaciation. 

The surface of the drift is very unlike that developed by the 



398 



ELEMENTS OF GEOGRAPHY 



erosion of running water, for in the latter the depressions have 
outlets, and the hills and ridges stand in a definite relation to the 

valleys. 

Thedrift left by the 
continental glacier in- 
creased the relief in 
some places (Fig. 288), 
with unfavorable 
results; but in most 
places it decreased re- 
lief and left the surface 
less rough than it found 
it (Fig. 289). This 
made it easier to culti- 
vate the land and to 
build roads. Most of 
the surface between the Ohio River and the Great Lakes appears 
to have been made smoother. But for glaciation, much of this 
region probably would have a maturely eroded surface, not unlike 
that of the driftless area, and a poorer soil than it now has. 




Fig. 285. A lateral moraine left by a former 
glacier in the Bighorn Mountains of Wyoming. 
(From photograph by Blackwelder.) 




Fig. 286. The Illecillewaet Glacier, British Columbia. 



Deposits beyond the land. Glaciers which descend into the 
sea may build submarine banks and even islands. Along the eastern 
coast of North America, these deposits may have reached the edge 
of the continental shelf in some places. Martha's Vineyard, Nan- 
tucket, and Long Island are composed largely of drift. The shel- 



MODIFICATION OF LAND SURFACES 



399 



tered waterway behind Long Island facilitated the development of 
maritime interests in southern New England. Indeed, Long Island 




Fig. 287. 
(Fenneman.) 



Terminal moraine topography near Oconomowoc, Wisconsin. 



Sound is said to have been "the most powerful single factor con- 
trolling the destiny of New England." 

Glacial lakes. The thousands of lakes in northern United 
States (Fig. 290) and 
Canada are nearly all 
of glacial origin. Some 
are in basins gouged 
out of the bed-rock 
(Fig. 291); some are 
in the unfilled portions 
of drift-choked pre- 
glacial valleys; and 
many are in hollows 
in the surface of the 
drift (Fig. 292). The 
terminal moraines of 
many valley glaciers 
form dams, ponding 
the waters of the 
streams above, making 
lakes (Fig. 293). The 




Fig. 288. Diagram showing how a nearly level 
surface may be replaced by a rough one through the 
uneven deposition of drift. 

Fig. 289. Diagram showing how glacial drift 
may replace a hilly surface with a comparatively 
level one. 



400 



ELEMENTS OF GEOGRAPHY 



smaller and shallower of these lakes and ponds are being destroyed 
rapidly by (i) the sediment washed into them from the tributary 




Fig. 290. Map showing the abundance of lakes in parts of the glaciated area. 
(From Barrett, Minnesota, Sheet, U. S. Geol. Surv.) 




Fig. 291. Section of a lake in an 
ice-scoured rock basin. 



slopes, and (2) vegetable matter (Fig. 294). Some are being drained 
slowly (Why slowly?) by the erosion of their outlets. In the future, 

many of the shallower ones will be 
drained by man, that he may use 
their bottoms as farm land. It has 
been estimated that there are 8,000 
lakes, big and little, in Minnesota, 
and that half of them will be de- 
stroyed by natural processes within 
fifty years. Connecticut has been 
credited with having had some 4,000 
lakes at the close of the Glacial 
Period; 2,500 of them have been 
obliterated, and the sites of many of 
them now form choice garden spots. 
In southern Michigan and Wiscon- 
sin many early settlers located their 
farms on the bottoms of former 
lakes, attracted by the flat land 
and the fine, easily-worked soil. 
Deposits of marl occur in and about many glacial lakes. Marl 
is a soft, limey earth, the calcium carbonate of which is contributed 
chiefly by the shells of fresh-water mollusks and by lime-secreting 




292. Section of a lake lying in a 
hollow in the surface of the drift. 




Fig. 293. Section of a lake behind 
a barrier of drift. 



MODIFICATION OF LAND SURFACES 



401 



lake plants. In parts of Michigan and northern Indiana, these 
deposits are utilized in making Portland cement. 

The lakes and swamps of the glaciated region make the streams 
flow more steadily through the year, by holding back some of the 
water of wet times, letting it flow out in times of drought. The 
drift itself exerts a similar influence, for, on the whole, it is thicker 
than the mantle rock of other regions, and therefore absorbs more 




Fig. 294. A pond in Yellowstone Park nearly destroyed by encroaching vege- 
tation. (Fairbanks.) 



water, which it yields up slowly, making the supply of ground- 
water to streams more steady than it would be otherwise. Thus 
floods are less numerous and less dangerous, and the value of the 
streams for navigation and power is increased. By reducing or 
preventing floods, the porous drift and the lakes also greatly reduce 
soil erosion. 

Certain lakes which came into existence along the margin of 
the continental glacier disappeared with the ice. One of the largest 
of the marginal lakes {Lake Agassiz) lay in the valley of the Red 
River of the North (Fig. 295). This lake covered a maximum area 
of about 110,000 square miles, an area greater than that of all the 
Great Lakes. The water, however, was shallow. It came into 
existence when the edge of the retreating ice lay north of the lake, 
and blocked drainage in that direction. The water rose in the 
basin until it overflowed to the south, finally reaching the Mississippi 



402 



ELEMENTS OF GEOGRAPHY 



River. When the ice at the north melted back far enough, a new 
and lower outlet was opened to Hudson Bay, and the lake was drained. 
Lake Winnipeg and several smaller lakes may be regarded as rem- 
nants of Lake Agassiz, for they occupy the deepest parts of the 
old basin. 

As late as 1870 the floor of extinct Lake Agassiz was practically 
unoccupied by farmers (Fig. 296), but during the next few years 



% i &tri>soJf $ ' 




pl'PEItlOji 



Fig. 295. Map of extinct Lake Agassiz, and other glacial lakes. Lake Winni- 
peg occupies a part of the basin of Lake Agassiz. (U. S. Geol. Surv.) 



its soil was found to produce a fine grade of hard wheat, and a great 
tide of farm-seekers turned to the region (Fig. 297). On the nearly 
level lake floor it was possible to plow league-long furrows in straight 
lines, and later to do much of the work by such labor saving machines 
as the steam plow. Ft. Gary quickly grew into the city of Winnipeg, 
and the wheat of the region helped to make Minneapolis the leading 
flour manufacturing city of the United States (p. 441). 

The Great Lakes were larger than now after the ice had retreated 



MODIFICATION OF LAND SURFACES 



403 



north of their basins, but while it still covered the lower St. Lawrence 
Valley. A part of their history, dating from the time when the 
last ice-sheet was waning, is suggested by Figs. 298 to 301. These 
lakes did not exist, so far as known, before the Glacial Period, but 
river valleys probably extended along their longer diameters. Lake 
basins were developed as a result of (1) the deepening of these valleys 
by ice erosion, N (2) the building up of the rims of the basins by the 



1870 'T """ " V ~-.._.^.. 

oil V, 

~^ a MINNESOTA 


L A ^A 


\jCj\^~~~~-~ ( r* 


DAKOTA ) V \^J-^y 


■ 




' >s sg5?^".^BI BBk - 


I - .. '■ 


JK~i J "i?«3 




Fig. 296. Fig. 297. 

Fig. 296. Map showing distribution of population in region of Red River of 
the North in 1870. 

Fig. 297. Population map of region of Red River of the North in 1880. 

deposition of drift, and perhaps (3) the down-warping of the sites 
of the basins. The influence of the Great Lakes on climate and 
on certain industries has been noted (pp. 79, 117, 145). Their im- 
portance as commercial highways is considered in Chapter XVI. 

Hundreds of the glacial lakes are of great benefit to man as 
pleasure and health resorts, and as sources of water supply. Many 
have become famous through their fine summer residences, and 
very many more are visited by numerous camping, boating, and 
fishing parties. In these ways the lakes have become large factors 
for good in the life of the people. 

The Iowa Waterways and Conservation Commission recently declared, with 
reference to the few lakes of that state, that the state government is "under 
evident obligation to care for them, to keep them as a trust for the people, and to 
see that they are not only not abused and rightly used, but to see to it that they 
are used with such wisdom, in all the resources they afford, as to be constantly 
more and more serviceable and valuable in every way." 



4°4 



ELEMENTS OF GEOGRAPHY 







Fig. 298. The beginning of the Great Lakes. The ice still occupied the larger 
parts of the present lake basins. (After Taylor and Leverett, U. S. Geol. Surv.) 



-J' 




Fig. 299. A later stage in the development of lakes Chicago and Maumee. The 
ice has retreated, and the outlet of Lake Maumee is being shifted. (U. S. Geol. Surv.) 



MODIFICATION OF LAND SURFACES 



405 



Effect of ice deposits on stream courses. The deposition of 
drift deranged the rivers. After the ice melted, the surface drain- 
age followed the lowest lines open to it; but these lines did not 
always correspond with the former valleys, for some of the latter 
had been filled, and most of them were blocked up in some places. 
The surface waters therefore followed former valleys in some cases, 




Fig. 300. The Great Lakes at the Algonquin-Iroquois stage, 
to the sea is by way of the Mohawk Valley. (Taylor.) 



The outlet 



and in others flowed where there had been no valleys. In choosing 
their new courses, the streams in places ran down steep slopes 
or fell over cliffs. Many of the rapids and falls of the glaciated area, 
so important in the economic life of the country (p. 440), came into 
existence in this way. 

Glacial soils. In the United States, glaciation increased the 
amount of mantle rock, and improved the quality of the soil in 
many places. Much of the latter is good because it is a thorough 
mixture of material derived from many kinds of rock, and so is 
well supplied with all the mineral elements necessary for plants 
(p. 270). In Illinois, the average productivity of the soils developed 
on the youngest drift sheet is greater than that of the soils of the older 
drift. (Suggest plausible reasons for this.) It is instructive to 



406 



ELEMENTS OF GEOGRAPHY 



compare Fig. 402, showing the relation of the improved acreage to 
the total farm acreage in the different states, with the map showing 
the glaciated area (Fig. 273). Iowa, Illinois, Indiana, and Ohio 
are seen to lead in the relative amount of their improved land. 
Glaciation is perhaps the most important fact in the geography of 
each of these states, and it has greatly furthered their high rank 
in agriculture. 

The benefits which the states between the Ohio River and the 
Great Lakes received from glaciation may be illustrated further. 




Fig. 301. A still later stage of the Great Lakes. The sea is thought to have 
covered the area shaded by lines at the east. (Taylor.) 



Fig. 302 shows the glaciated and unglaciated portions of Ohio. The 
unglaciated part belongs to the Alleghany Plateau. It is in a mature 
stage of erosion, and the thin, sandy soils on the steep slopes wash 
easily. The first settlement in Ohio was made in this part of the 
state, at Marietta; but soon the tide of settlement set toward the 
more attractive glacial plains farther west and north, and the popu- 
lation of most of the unglaciated counties remained relatively sparse 
until the mineral resources of the region were developed. Many 
farmers in the unglaciated section turned their attention to sheep- 



MODIFICATION OF LAND SURFACES 



407 



raising when they found they could not grow grain for export in 
competition with the glaciated farms, and grazing was long an im- 
portant industry in the southeastern part of the state. 

About four-fifths of Indiana were glaciated. On the average, 
the glaciated land is worth about twice as much as the unglaciated, 
and the yields of staple crops bear a similar relation. The south- 
ern boundary of the region within which 4,500 bushels of corn are 
grown per square mile, is the 
margin of the latest drift sheet. 
The situation is much the same 
in Illinois. Fig. 303 shows the 
yield of corn (the leading crop) 
throughout the state. The rela- 
tions of the yield to the several 
sheets of drift, whose borders 
are indicated by the irregular, 
heavy lines, are striking. The 
low yield of the unglaciated 
areas at the extreme south and 
northwest is noteworthy. 

The quality of the soil in 
some places was injured by 
glaciation. In some places the 
drift is very thin, while in others 
it is very stony (Fig. 1 50) , so that 
great labor is necessary to put it 

in workable condition. Again, the drift may be too sandy or gravelly 
to make good soil, or its surface may be too rough (pp. 275, 396). 

Special uses of glacial deposits. Much drift clay (rock flour) 
is used for making brick, tile, and other clay products. Ohio has 
been the leading state in the clay industry for many years, because 
of the abundance of raw clay, part of which is drift, cheap near-by 
fuel, excellent shipping facilities, and nearness to great markets. 
About 1,000,000,000 bricks are made from glacial clay each year 
in the vicinity of Chicago. The gravel of the drift is used exten- 
sively for road making, and in the manufacture of various kinds of 
cements. 

DEPOSITS BY GLACIAL WATERS 

Water flows in abundance from all glaciers in the summer, and 
from many glaciers all the time. Stream work, therefore, accom- 




Fig. 302. Map showing the glaciated 
(shaded) and unglaciated portions of Ohio. 



4o8 



ELEMENTS OF GEOGRAPHY 



panies glaciation in all cases, and much of the drift left by ice is 
modified by water afterward. 

Streams which flow from glaciers carry so much sediment that 
in many cases they build gravelly or sandy plains beyond the ice. 
Such a deposit in a valley below a glacier is a valley train. Valley 

trains are developed best just 
outside terminal moraines. 
The Rock River, in southern 
Wisconsin, filled its valley with 
gravel and sand to a depth of 
300 to 400 feet just outside the 
terminal moraine of the last 
glacial epoch. The Columbia 
River filled its valley, locally, 
to the depth of 700 feet with 
sediment washed out from the 
ice. Since the ice-sheet melted, 
parts of most of the valley 
trains have been carried away, 
and their remnants are terraces 
(Fig. 262). Drift terraces are 
common features of many of the 
valleys of south-flowing rivers 
in the glaciated area and just 
south of it. 

Streams which issue from an 
ice-sheet and fail to find valleys 
build alluvial fans. By growth, 
these fans may unite, making an 
outwash plain, very much like a 
compound alluvial fan. Like 
valley trains, outwash plains are developed best just outside the ter- 
minal moraines of ice-sheets, and their materials are stratified. East 
New York, Woodhaven, Jamaica, and other suburbs of Brooklyn 
grew up on the outwash plain of Long Island before the terminal 
moraine just to the north was much settled. (What were the prob- 
able reasons for this?) 

Deltas may be built in lakes at the ends or edges of glaciers, 
and the deposits made by waters beneath the ice and at its edge 
take on locally the form of ridges and hillocks. 




Fig. 303. Map showing average yield 
of corn per acre throughout Illinois. 



MODIFICATION OF LAND SURFACES 409 

As a glacier melts away, the waters produced by the melting 
flow over the surface of the drift which the ice had deposited, and 
modify it more or less by eroding in some places and depositing 
in others. As a result of all these phases of. water work, much of 
the drift is stratified. 

EFFECTS OF ANCIENT ICE-SHEETS ON LIFE 

The continental ice-sheets caused extensive changes in the life 
and the life relations of higher latitudes. The development of the 
first great ice-sheet in our continent, for example, killed all plant 
life over the millions of square miles which the ice covered, and 
drove all animal life from the region. Most of the types of plants 
which had grown in the north before the Glacial Period probably 
continued to live, but they lived farther south. 

Though a tree or a shrub cannot migrate, a given type of tree 
or shrub may migrate through its seeds. In the course of many 
generations, Arctic plants migrated southward in front of the edge 
of the slowly-advancing ice-sheet, while those that had lived in 
middle latitudes were driven still farther toward the equator. 

Animals, moving more freely than plants, were able to migrate 
as individuals. As the ice-sheets grew, the animals of the north 
doubtless crowded southward. This migration from the north 
into middle latitudes drove the animals of the latter still farther 
south. If similar changes were taking place in the southern hemi- 
sphere, as seems probable, there was a tendency to crowd life into 
low latitudes from both sides, and no parts of the continents, not 
covered by ice, were free from the effects of migration and crowd- 
ing. Animal life migrated from North America to South America 
by way of Central America and the Isthmus of Panama, and corres- 
ponding migrations affected the eastern hemisphere. The lessening of 
the area of land on which animals and plants could live must have de- 
creased greatly the total amount of plant and animal life on the earth. 

When the first ice-sheet melted, the area left bare was again 
peopled by plants and animals moving poleward from lower lati- 
tudes. The time necessary for the melting of an ice-sheet was 
perhaps as long as the time necessary for its growth — many thou- 
sands, probably many tens of thousands of years — so that the 
redistribution of animals and plants over the area which had been 
glaciated, was slow. Before the drift left by the ice was covered 
with vegetation, the blowing of dust must have been very extensive, 



4 io ELEMENTS OF GEOGRAPHY 

and the surface must have been subject to much greater erosion 
than now by water. 

As the ice receded northward, the Arctic plants which had been 
driven south followed it; but in mountainous regions, some moved 
up the mountains instead of moving northward. Thus it came 
about that plants whose ancestors lived in Arctic regions are now 
found high in the mountains of middle latitudes. They probably 
lived in the lowlands of these latitudes during the glacial epoch, 
and found the colder temperatures to which they are adapted higher 
up on the mountains, as the climate again became warmer. 

The life of the sea was affected similarly, though perhaps less 
extensively than that of the land. The northern waters must have 
been distinctly colder than now. 

Each glacial epoch in turn produced similar effects, so that the 
Glacial Period was one of great importance to all life. 

Summary. Although less important, ice takes its place with air 
and water as one of the three agents which modify land surfaces. 
From this standpoint, its principal mission is the wearing of the land 
and the moving of the waste toward the sea. Through their wide- 
spread effects on topography, soil, drainage, and the distribution of 
plant and animal life, the ancient ice-sheets are far more important 
than the glaciers of to-day, as factors in human affairs. Existing 
glaciers are valuable to man chiefly in connection with the de- 
velopment of power on the streams which flow from them. 



QUESTIONS 

i. In northern United States and Canada, would floods which occur as the 
river ice breaks up in spring be more likely to be disastrous on north-flowing or 
south-flowing streams? Why? 

2. Why are there more glaciers in the Sierra Nevada and Cascade moun- 
tains than in the Rocky Mountains? Why are there more in Montana than 
in Colorado? 

3. Enumerate all the factors which may influence the size of a given valley 
glacier. 

4. Compare and contrast typical topographies due to (1) glaciation and (2) 
river erosion. 

5. (1) What are all the important ways in which human interests have been 
(a) benefited and (b) injured by the work of the ancient ice-sheets in the United 
States? (2) On the whole, was glaciation beneficial or injurious? 

6. Why are the effects of glaciation more favorable, from the standpoint 
of man, in northern United States than in northeastern Canada? 



MODIFICATION OF LAND SURFACES 



411 



7. (1) What are the possible ways in which the topography shown by Fig. 
304 may have originated? (2) Which is the most probable way? Why? (3) 
How could you settle the matter in the field? 




Fig. 304. View on Staten Island. (Willis, U. S. Geol. Surv.) 



REFERENCES 

Brigham: The Fiords of Norway, in Bull. Am. Geog. Soc, Vol. XXXVIII, 
PP- 337-348. 

Chamberlin: The Rock-Scorings of the Great Ice Invasions, in 7th Ann. 
Rept., U. S. Geol. Surv., pp. 147-248. 

Davis: Glacial Erosion in France, Switzerland and Norway, in Proc. Bost. 
Soc. Nat. Hist., Vol. XXIX, pp. 273-322. 

Davis: Hanging Valleys, in Science, N. S., Vol. XXV, pp. 833-836. 

Geikie, J.: Land-Forms Modified by Glacial Action, in Earth Sculpture, 
Chs. X, XL (New York, 1898.) 

Geikie, Sir A.: Scenery of Scotland, Chs. IV, X, XI, XIV, XVII. 3d ed. 
(London, 1901.) 

Gilbert: Alaska; Glaciers and Glaciation. Vol. Ill of Ha'rriman Alaska 
Expedition. (New York, 1904.) 

Nansen: The First Crossing of Greenland. (London, 1893.) 

Peary: Northward Over the "Great Ice." 2 vols. (New York, 1898.) 

Russell: Glaciers of North America. (Boston, 1897.) 

Russell: Malaspina Glacier, in Jour, of Geol., Vol. I, pp. 219-245. 

Salisbury: The Drift, in Jour, of Geol., Vol. II, pp. 708-724, 837-851; 
Vol. Ill, pp. 70-97. 

Salisbury: The Glacial Geology of New Jersey; N. J. Geol. Surv., Vol. V. 

Tarr: Physiography and Glacial Geology of the Yakutat Bay Region, Alaska; 
Pt. I, Prof. Paper 64, U. S. Geol. Surv. 

Many of the topics of this chapter are discussed at greater length in standard 
textbooks of physiography and geology. (See p. 312.) 



CHAPTER XVI 
THE USES AND PROBLEMS OF INLAND WATERS 

Many ways in which streams and lakes affect human interests 
have been noted in preceding pages. In the present chapter, inland 
waters are considered from the standpoints of navigation, power, 
irrigation, drainage, and water supply. 

Navigation 

In the early development of many countries, lack of roads led to 
the use of the waterways for trade and travel. Even after roads 
and turnpikes had been provided, water transportation was, in 
general, much cheaper, and traffic continued to use waterways 
where they were available. A horse that could draw one ton 
on a good road in a cart could draw thirty to forty tons in a 
canal boat. In the United States, the average cost of hauling a 
ton a mile over roads is now about twenty-three cents. At this 
rate, it costs the farmer more per bushel to haul wheat 10 miles 
to a railroad than it costs the buyer to ship it from New York to 
Liverpool. 

Where railroads have come into competition with waterways, 
the latter in most cases have lost much of their traffic. The water- 
ways of some countries have been protected by legislation from 
ruinous railroad competition, and certain waterways, for example 
the Great Lakes, furnish such favorable conditions for transporta- 
tion that their traffic has grown in spite of railroad competition. 
The average cost of hauling over the railroads in the United States 
declined from 7^ cents a ton per mile in 1837, to less than 4 /s of 
a cent a mile in 1905; yet under favorable conditions, the cost of 
transportation by water is estimated to be only ^ to ^ that by 
rail. In 1909, rates for iron ore on the Great Lakes were less than 
one mill a ton per mile, while the rates for ore by rail were about 
one cent a ton for the same distance. 

412 



USES AND PROBLEMS OF INLAND WATERS 413 



RIVER NAVIGATION 

Streams the first waterways used systematically. Naturally, 
streams were the first waterways to be used systematically for com- 
merce (Why?). The Euphrates was one of the rivers to which men 
first entrusted themselves and their goods. Sculpturing on the 
Assyrian monuments shows that the first boats had frames of light 
wood, covered with skins. These boats could not ascend against 
the strong current, and therefore were used only for down-river 
trade. They were broken up on the lower river, the wood sold, 
and the skins carried by asses on the return journey. There was 
also very early traffic on the Nile River. 

After a time, river navigation led to coastwise navigation, but 
to the end of the Mediaeval Period there was little or no navigation 
of the open ocean. It is only in the Modern Period that open sea 
navigation has permitted the development of world commerce and 
an "oceanic civilization." 

Leading rivers of other countries. Because of its relief (p. 41), 
few of the rivers of Asia are important highways of commerce. 
The Yang-tze is the greatest highway. Fed by the snow-fields of the 
mountains of Tibet, and flowing to the Pacific through some of the 
most densely populated provinces of China, it is both one of the long- 
est rivers in the world, and one of the most important commercially. 
Large ocean steamers ascend 600 miles to Hankow; smaller steamers 
navigate the river 500 miles farther, to the mouth of the gorges; 
and native junks go up many miles more into the rich province of 
Sze-chuan. The Yang-tze is the greatest highway between western 
and eastern China. The Hwang-ho, the other great river of China, 
flows through a densely settled region, but is nearly useless for 
navigation because of its shifting and silt-choked channel. 

In India, the Ganges and Indus present a contrast similar to that 
of the Yang-tze and Hwang-ho. The Ganges traverses the most 
populous and wealthy provinces, and has been of great significance 
throughout the history of India. It is fed by many Himalayan tor- 
rents, and flows for about 1,200 miles across the alluvial plains of the 
north. Ocean steamships ascend the Hugh, one of the mouths 
of the Ganges, to Calcutta, and, though it has suffered from rail- 
road competition, the river is used more or less for navigation to 
Hardwar, at the base of the mountains. The Indus River is used 
but little by steamers, because of many sand bars and frequent 



4H ELEMENTS OF GEOGRAPHY 

changes in the channel. Together with its larger tributaries, it is 
valuable chiefly for irrigation. The great rivers of Siberia are navi- 
gable for hundreds of miles, but lose in commercial importance because 
they flow to the Arctic Ocean. 

The relief of Africa limits the navigation of most of its rivers to 
relatively short distances (p. 41). The Nile has regular steamboat 
service to the First Cataract, but navigation is not easy in the delta 
portion of the river below Cairo. Above the cataracts, the river is 
navigable throughout the year for long distances. 

Throughout the history of Russia its rivers have been its chief 
highways. Even to-day, they have greater relative importance 
than the rivers of western Europe, because other means of trans- 
portation are less satisfactory; wagon roads are poor and railroads 
few. Most of the Russian rivers rise in the vicinity of the Valdai 
Hills and follow long courses across low, nearly level plains. Their 
currents, therefore, ordinarily are gentle. They are navigable through- 
out most of their courses, and it has been possible to connect the 
different systems by canals, so that there is water connection between 
the Caspian, Black, Baltic, and White seas. While the above 
conditions are favorable to commerce, navigation of the Russian 
rivers is attended by serious drawbacks. They are ice-locked in 
winter (p. 380), subject to great floods when the snows melt in spring, 
affected by sand bars which hinder navigation at low stages, and 
most of them are tributary to inland seas. The Volga is the most 
important Russian river, and the largest river of Europe. Together 
with its tributaries, it is said to afford 7,500 miles of navigation. Its 
usefulness is lessened by the fact that it flows in its lower course 
through a semi-arid region, and ends in a land-locked sea. 

Most of the larger rivers of central and western Europe are 
important commercially, and large sums have been spent to improve 
them, and extend their connections by canals. In the last fifty 
years not less than $1,000,000,000 have been expended in France, 
Belgium, Holland, Germany, Austria-Hungary, and Italy, in an 
area smaller than the part of the United States east of the Mis- 
sissippi River. In Germany, river transportation increased more 
than five- fold in the thirty years preceding 1905, in spite of the 
fact that Germany has a greater railroad mileage than any other 
country in Europe. This is in striking contrast with the situation 
in the United States (p. 425). The rivers and canals of Germany 
(p. 437) furnish from 8,000 to 10,000 miles of navigable water- 



USES AND PROBLEMS OF INLAND WATERS 415 

ways. So much work has been done in dredging, straightening, 
and otherwise improving the larger rivers, that it is said scarcely one 
of them flows in a natural channel. 

The Rhine has influenced the history of Germany more than any 
other river, and is to-day the most important commercial river in 
Europe. Fed by melting snows in Switzerland and regulated in 
volume by its passage through Lake Constance, it flows through 
western Germany and the Netherlands, into the North Sea. Rot- 
terdam, on the Rhine delta, is one of the greatest ports of 
continental Europe, and Cologne, though far inland, is practically a 
seaport. The fertile valley of the Rhine is settled densely, and prob- 
ably there are more important cities on its banks than on an equal 
length of any other river. The Elbe is commercially the second river 
of Germany, though much less important than the Rhine. The 
traffic on these rivers is largely in heavy freight, such as coal and 
grain. (Why are the cities on the lower courses of the German rivers 
flowing into the Baltic Sea less important than those situated simi- 
larly on the rivers flowing into the North Sea? Is this difference 
likely to continue?) 

The Danube River has been an important highway since early 
times. Like many other delta-building rivers, it was difficult to 
enter until jetties were built at its mouth. Extensive improvements 
have been made also at the "Iron Gate," and elsewhere. The Rhone 
is the largest river of France, and its valley is the natural highway 
into the country from the south. Navigation in the delta portion of 
the stream was impeded by shallow and shifting channels, and canals 
have been constructed from the sea to the river near the head of the 
delta. Though large sums have been spent in these and other im- 
provements, the Rhone is not navigable for large ships. The Po and 
the Ebro are the only other European streams of importance emptying 
into the Mediterranean, and neither is used much for navigation. 

In Great Britain, the rivers are comparatively short, but their 
value is enhanced by the fact that their lower courses are drowned, 
and subject to rather high tides. The tides help to make Liverpool 
and London great seaports, though both are on small rivers. Like the 
United States, great Britain has neglected, till recently, the question 
of waterway improvement, in part because of the nearness of ocean 
transportation, the expense of canal construction, and the influence 
of the railroads. To-day transportation in England is said to be the 
most expensive in Europe. 



416 



ELEMENTS OF GEOGRAPHY 



The Amazon is the largest river in the world, with a length of 
about 4,000 miles. Ocean steamers can ascend it for 1,000 miles, 
and with its 29 large tributaries it furnishes more than 20,000 miles 
of navigable water, most of it through dense forests. The river is 
used in getting out tropical woods, rubber, and other products. The 
Orinoco is navigable to within 100 miles of Bogota, and the La Plata 
system is navigable for long distances, especially for light-draft boats. 




Fig. 305. Map showing principal streams in the United States actually used 
for purposes of transportation (1906). Only the sections so used appear on the 
map. (Data from map by U. S. Bureau of Corporations.) 

Besides the great rivers mentioned above, there are many others 
which serve as highways of trade and travel that it is not practicable 
to consider here. 

Navigable streams of the United States. There are about 300 
streams in the United States that are navigated more or less (Fig. 
305). They have a combined navigable length of about 26,400 
miles — more than the circumference of the earth. Only a few 
now have much commercial importance, and many are frequented 
only by small boats engaged in local trade. As Fig. 305 shows, 
most of the navigable streams are in the eastern half of the country. 
The absence of navigable waterways (Why absent?) has been a 
serious disadvantage to much of the West. 



USES AND PROBLEMS OF INLAND WATERS 417 

The principal rivers, and the part which they have played in 
the development and commerce of the country, are discussed briefly 
in the following paragraphs. Most attention is given to the Mis- 
sissippi System, because it is by far the most important. 

Atlantic Rivers of United States 
On the Atlantic slope there are nearly 150 streams navigable 
for varying distances from the sea — in most cases to the head 
of tide-water. The rivers of New England are navigable for short 
distances only, because of falls and rapids. 

The Connecticut is navigable 50 miles, to Hartford; the Merrimac 17 miles, 
to Haverhill; the Saco 5 miles, to Saco and Biddeford; the Androscoggin 30 miles; 
the Kennebec 44 miles, to Augusta; and the Penobscot 60 miles, to Bangor. All 
these cities receive much freight by water. Many streams of central and northern 
New England are used for rafting lumber and floating logs. 

Although the streams of New England afford little navigation, the larger val- 
leys have been important highways since the settlement of the region began. They 
guided fur traders, lumbermen, and farmers (p. 340) into the interior. They 
served as lines of advance and retreat for numerous Indian war parties and colonial 
armies. General Arnold invaded Canada in 1775 by way of the Kennebec and 
Chaudiere valleys. To-day, many of the valleys are followed by railroads. Since 
the rivers could not serve as highways far inland, the colonial authorities provided 
promptly for the opening of roads. Partly for the same reason, the main lines 
of the New England system of railroads were completed before those of any other 
section. Boston was handicapped greatly in its commercial development by the 
fact that no large, navigable river led from it into the interior. 

The Hudson is the most important, commercially, of the tribu- 
taries to the Atlantic from the United States. Because of the drown- 
ing of the Hudson Valley, deep water extends 100 miles from the 
mouth, and the river is navigable 50 miles farther, to Troy. 

The belt of relatively weak rocks along which the Hudson Valley developed 
contains, farther north, Lake Champlain and the Richelieu River. This long, 
narrow lowland, which extends from New York City to the St. Lawrence River 
near Montreal, was called by the Indians "The Grand Passway." General 
Burgoyne (1777) and General Prevost (1814) used it to invade the United States. 
When the Champlain Canal was opened between the Hudson River and Lake 
Champlain, water transportation was available throughout its entire length. 
The Mohawk Valley and the low plain to which it leads furnish an easy route 
between the Hudson River and Lake Erie; the highest point is only 445 feet above 
sea-level. Its drowned-valley harbor and unparalleled connection with the 
interior have been leading factors in the growth of New York City. 

South of the Hudson River, most of the larger rivers are 
navigable to the "fall line," where the streams, in passing from 



4i8 



ELEMENTS OF GEOGRAPHY 



the hard, crystalline rocks of the Piedmont Plateau to the weak, 
stratified rocks of the Coastal Plain, have developed falls and rapids. 
Along this line are Philadelphia, Baltimore, Richmond, Petersburg, 
Raleigh, Columbia, Augusta, Macon, and Columbus (Fig. 306). 
Ocean-going vessels ascend the Delaware River to Philadelphia, and 
smaller boats go up as far as Trenton. Several drowned tributaries 

of Chesapeake Bay have some 
commercial importance. 

The drowned streams of the Vir- 
ginia region were deep enough to 
accomodate the light-draft boats of 
the colonial period, and served the 
settlers as roadways. The planta- 
tions were arranged in narrow belts 
along the stream courses. For a cen- 
tury, travel in tidewater Virginia was 
largely by water; little attention was 
given to road building. Ships came 
from England direct to the wharves 
of many of the plantations, to ex- 
change for tobacco the manufactured 
goods needed in the colony. Under 
these circumstances, no important 
collecting and distributing centers 
developed. To 1700, Jamestown was 
the only place worthy of being called 
a village. Laws were passed for the 
care of the all-important waterways; 
ships on coming to anchor were not 
permitted to throw their ballast into 
the channel, and trees that toppled 
into the streams were to be removed 
promptly. In South Carolina, the 
streams were not drowned sufficiently 
to render many of the smaller ones navigable. Hence Charleston became the 
commercial center of the colony, and soon also the social and political center. In 
general, freight rates decrease as the size of the cargo increases, and accordingly 
the tendency has been to build larger and larger boats. As a result, many of the 
streams of the Coastal Plain, once important in trade, were long since abandoned 
by commerce. 

Mississippi River System 

The Mississippi river system is by far the most important in 

the United States (Fig. 305). The main river has more than 50 

tributaries that were navigated more or less in 1907. The navigable 

waters of the system aggregate nearly 14,000 miles, and border or 



p-("']f^\ 


New York 




- - *~~Z£^^ \ 


Trenton '•(' 




\ 
) 


Philadelphia nT 
, ••- Baltimore fFQ v \ 


Jj 


) 


Washington* J c| \j 




/"'* 


■ \^^§^\ri 




••■x ,. v ) 


i'\: \ ~%/V Yi 




/ \ ^L {v 




! 


1 Petersburg ^Ij^C V>' 
y Richmond J^« 




\ 




.* 


,.•"' / . jA 




/ *■*..-•' 


___ ..-J[r — *L ^ 




^a. r- 

. / 


VPa]eigh<* = ^<- 


9) 


fv" 




1 


S 






("" 


""• / --N A 










' 1 


N s I 










1 \ 


•Oioluinbia f 






^Augusta "f 




\ •''Macon 


SW 




^Columbus 






jt 


i \ 






" «\ 





Fig. 306. Map showing leading cities 
along the "fall line." 



USES AND PROBLEMS OF INLAND WATERS 419 

traverse 21 states. The Mississippi River itself is navigable for 
large steamers and barges from its mouth to St. Louis (1,256 miles), 
and for smaller boats to St. Paul (729 miles farther). The Ohio 
River, now much the most important, commercially, in the United 
States, is navigable throughout its length of 967 miles. The Mis- 
souri River is navigable for small boats to Ft. Benton, in Montana, 
but now is used but little. Other tributaries of the Mississippi are 
navigable for varying distances, as shown by Fig. 305. 

Influence on early development of the West. At the close 
of the Revolutionary War, the Mississippi River was made the 
western boundary of the United States, and the supposed length of 
the river set the initial width (north and south) of the country. 

The Mississippi River was an unsatisfactory international bound- 
ary line, for (1) its position shifts (p. 368), (2) the navigation of the 
river by the Americans from the east side and any foreign people 
from the west side would have led to friction, and (3) the river basin 
is a natural unit. Until 1803, the ultimate ownership of the basin 
was in doubt. At different times the plans of Spain, France, and 
England looked to getting the eastern part of the basin as well as 
the western. To the American settlers along the Ohio River and 
its tributaries, the free use of the lower Mississippi as an outlet to 
market was of the greatest importance. Disgusted at the attitude 
of the government in its negotiations with Spain, which controlled 
the mouth of the Mississippi River and at times closed it to them, 
many of the western frontiersmen considered leaving the Union 
and attaching themselves to one of the European powers mentioned 
above, in order to secure the free navigation of the river. Their 
willingness to do this reflects not so much their lack of patriotism, 
as their commercial dependence upon the western rivers, and 
their isolation from the older section by the Appalachian Mountains. 
That the political unity of the Mississippi Basin was brought about 
by the advance of the American boundary toward the west, rather 
than by its retreat to the Appalachian Mountains, was due largely 
to the strength and sweep of the westward advance of American 
settlers, and to the turn of European politics. 

The early western settlers could send over the difficult mountain 

roads to the eastern seaports only valuable articles of little bulk and 

weight, such as whiskey, furs, and ginseng, or live stock, which could 

walk to market. For years, many thousands of hogs and cattle 

were driven over the mountains to Charleston, Baltimore, and 
: 



420 



ELEMENTS OF GEOGRAPHY 



Philadelphia, but salted and dried meats, flour, tobacco, and the other 
export products of the frontier had to go down the Mississippi River 
to New Orleans. Roads were few and poor, and the settler found 
it highly desirable to locate his farm within easy hauling distance 
of a navigable stream. The influence of navigable waterways upon 
the distribution of population is shown clearly by the census map: 
of 1820 (Fig. 439), and several later years. 

One of the most used of the early boats on the western rivers 
was the flatb oat, commonly 15 feet wide (said to be the maximum 




Fig. 307. A typical flatboat. 

width which could pass through the rapids of the Ohio River at 
Louisville), and 40 to 50 feet long (Fig. 307). While these boats 
served for down-stream navigation, they were almost useless against 
the current of the Mississippi. Ordinarily they were broken up and 
the lumber sold at New Orleans. In these early days, freight was 
carried up-river largely in keel boats or barges. Most of them were 
equipped with oars, poles, and sails, and in many cases were dragged 
laboriously up-stream by men on the bank, tugging at a long rope. 
The average length of the trip from New Orleans to Louisville was 
three months, and in many cases it required four months. 

Influence of steam navigation on the development of the 
Interior. The first steamboat appeared on the Ohio River in 181 1, 
and by 181 7 it was apparent that steamers could cope successfully 
with the currents of the rivers of the Interior, and that they would 
increase greatly the commercial value of the streams. For a time, 
steamboats could not be built fast enough to take care of the business. 
In 1820, there were 72; in 1826, 95; in 1829, more than 200; in 1830, 
230; by 1843, 600; and in 1848, 1200. During these years the steam- 

■1 



USES AND PROBLEMS OF INLAND WATERS 421 

boats (Fig. 308) were changed greatly with a view to adapting them 
to the conditions of the inland waters. In 1835, the drdinary 
Mississippi River steamboat was about 150 feet long, 18 feet wide, 
and drew 6 feet when loaded. In 1855, when steamboat building 
had been perfected, the better boats were 225 or more feet long, 
about 35 feet wide, and drew when loaded 48 or 50 inches. These 
changes meant (1) greater capacity, (2) greater speed, (3) less steam 




Fig. 308. Mississippi River steamboats at New Orleans. 

in proportion to size and load, (4) less danger of grounding, (5) a 
great extension of the navigable waters, and (6) a great reduction 
in the cost of travel and transportation. By 1850, the time involved 
in up-stream travel had been reduced to about V18 of what it had 
been before the appearance of the steamboat. This meant, for 
example, that the steamboat brought New Orleans nearly as close 
to St. Paul, for certain purposes, as it had formerly been to Baton 
Rouge. The cost of travelling by water from New Orleans to Pitts- 
burgh before the advent of the steamboat is said to have been about 
$160. In 1830, steamboats offered cabin passage and food for the 
same trip for $35 to $45. Deck passage, without food, was much 
cheaper. In general, the steamboat soon reduced freight charges to 
about yi of what they had been, and finally to X ar >d less. Because 
of these things, steamboat navigation became one of the greatest 
factors in the development of the Interior. 



I 



422 ELEMENTS OF GEOGRAPHY 

The population of the Interior, commercially dependent for the 
most part on the rivers, increased from 2^ millions in 1820 to 43/5 
millions in 1830 and 6}i millions in 1840. Probably no single factor 
contributed more than the steamboat to the rapid expansion of 
population during these years. Thousands settled along the tribu- 
taries of the Mississippi having steamboat service, and almost over- 
night river towns sprang up at favored points. The total value 
of the commerce of the western rivers in 1S50 was estimated at 
$550,000,000. 

The leading centers of steamboat trade. During the period 
of steamboat supremacy, the river commerce of the Interior gravi- 
tated largely toward four commanding centers — Pittsburgh, Cin- 
cinnati, St. Louis, and New Orleans. 

For some time before the opening of the Erie Canal (1825, p. 434), 
Pittsburgh was the eastern gateway to the Mississippi Basin. Im- 
portant roads connected it with the eastern seaboard. In 1818, 
the merchandise carried by wagon to Pittsburgh from the East was 
valued at $17,885,000. The position of the city at the junction of 
the Monongahela and Allegheny rivers gave it many advantages. 
The former brought coal from West Virginia, while the latter gave 
it command of the white pine of western New York. About 1833, 
some 33,000,000 feet of lumber descended the Allegheny River to 
Pittsburgh each year. The principal products of the Pittsburgh 
mills during these years reflect these advantages, together with the 
command of iron and the products of the surrounding farms. They 
were implements and machinery, iron ware, cabinet ware, lumber, 
furniture, flour, and liquors. These things were sent by river through- 
out the Interior. 

Cincinnati had several marked advantages for the develop- 
ment of river trade. Situated mid-way on the Ohio and near the 
northernmost point of the great bend of the river, it is the nearest 
important river town for a large and fertile region north of the Ohio. 
It is also opposite the Licking Valley in Kentucky. The deep 
channel and favorable bank of the river along the entire city front 
gave it special facilities for handling steamboat traffic. It was 
connected (in 1832) by canal with Lake Erie (Fig. 317). By 
river Cincinnati received most of the implements and supplies, or 
the materials for their manufacture, needed by the tributary farm- 
ing region. By the same means were shipped the products of her 
flour mills, breweries, distilleries, and slaughtering and packing 



USES AND PROBLEMS OF INLAND WATERS 423 

houses, which had been established to use the products of the sur- 
rounding country. (Why was it desirable to manufacture these 
things near the points where the grain and animals were produced?) 
These advantages enabled Cincinnati to become the leading city 
of the Ohio Valley. 

For years most of the capital and business enterprise of St. 
Louis were engaged in the river trade, though later the city became 
an important manufacturing point. The following were the chief 
advantages which made it, next to New Orleans, the greatest steam- 
boat center on the Mississippi system. (1) It is situated near the 
mouths of the Missouri, Illinois, and Ohio rivers. (2) There is 
a significant difference in the depth of the Mississippi River above 
and below St. Louis (Fig. 309). At St. Louis, therefore, cargoes 
were exchanged between the lighter-draft boats of the upper river 
and those of heavier draft operating on the lower river. 

Because of its commanding position near the mouth of the Mis- 
sissippi River, New Orleans had for years the greatest commerce 
of any city west of the Appalachian Mountains. The population of 
New Orleans more than doubled between 1830 and 1840, in spite 
of the growing sand bars at the mouths of the river, frequent inun- 
dations, and disease (p. 376). No other important American city 
grew so fast. But even before the Civil War, the commerce and 
growth of New Orleans had received several serious blows. When 
canals were opened between the Great Lakes and the Ohio, Wabash, 
and Illinois rivers (p. 436), enormous quantities of goods from Ohio, 
Indiana, Illinois, and even from parts of Iowa and Missouri, sought 
the eastern markets by way of the Great Lakes and the Erie Canal, 
rather than the southern markets. New Orleans particularly was 
injured as an importing city. It is some 1500 miles farther than New 
York from the industrial centers of northwestern Europe, and the 
connection of New York with the Interior by way of the Hudson 
River, Erie Canal, and Great Lakes was superior to that of New 
Orleans against the current of the Mississippi. The railroads con- 
tinued the work of the canals, and made trade along east-west lines 
vastly greater than that along north-south lines. 

In addition to the four cities mentioned, many smaller cities 
and villages depended largely on river transportation and trade. 
Such were Louisville, whose location was determined by the rapids 
of the Ohio River; Nashville and Kansas City, profiting commercially 
(Why?) from their respective positions on the great bends of the 



424 



ELEMENTS OF GEOGRAPHY 







Ph 



USES AND PROBLEMS OF INLAND WATERS 425 

Cumberland and Missouri rivers; and Peoria, the leading city of 
the Illinois Valley. 

Decline of river navigation. For years, commerce on the 
Mississippi River and its tributaries has been relatively insignifi- 
cant in amount. The decline began at different times on different 
rivers — for example, in 1855 on the Illinois River, and about 
1883 on the Yazoo River. The causes of the decline also differed 
somewhat, but the leading ones were of general application. (1) 
The channels of many of the rivers were shallow, crooked, and 
shifting. (2) The depth of water varied much from time to time, and 
from place to place (Fig. 309). For the latter reason alone, there 
could not be a unified transportation system. Boats suited best 
to the conditions of the Great Lakes or coastwise trade could not 
be used on rivers or canals affording but 6 feet of water, and boats 
giving the most economical service for 6 foot channels could not 
be used in shallower waters, and so on. This was especially serious 
because of the importance of through traffic in American trans- 
portation. The great size of the United States and the high degree 
of industrial specialization in its different parts mean that much 
freight must move long distances. (3) The use of the rivers forced 
freight in many cases to take indirect, roundabout courses. (4) 
The waterways in the central and northern parts of the country were 
closed for a part of each year (p. 380). (5) Water transportation 
was relatively slow. (6) In general, the methods, terminal facili- 
ties, etc., of river and canal trade have remained unimproved since 
the Civil War, and have been less and less able to meet the demands 
of modern business. (7) When railroads were built throughout the 
Interior, these conditions proved fatal to the river trade. The rail- 
roads at once obtained most of the passenger trade, and most of the 
traffic in perishable and expensive freight. The rivers could, and in 
the future can, hope to compete only in the transportation of heavy, 
bulky, and non-perishable commodities such as coal, grain, lumber, 
building stone, and the like. It is highly desirable that the naviga- 
tion of the larger rivers be improved, so that they may assist the 
railroads in transporting the ever-increasing quantities of cheap 
freight (p._43 8 )- 

Even since the loss of most of their business, many of the water- 
ways have been of importance in regulating railroad freight rates. 
Most of the river towns that obtained good railroad connections 
did not suffer greatly from the decline of river trade; but to river 



426 ELEMENTS OF GEOGRAPHY 

towns without railroads the passing of the steamboat was a serious 
blow, and many such places decreased in population. 

Present traffic. The Ohio and its tributaries now have the 
largest river trade in the country, and Pittsburgh is the leading inland 
city in the volume of its river commerce. The traffic is mainly in 
coal (brought from West Virginia on the Monongahela and Kanawha 
rivers), lumber, logs, sand, and gravel. On the upper Mississippi, 
the declining traffic is largely in rafted logs and lumber, and in 
sand. The principal commodities transported on the lower Mis- 
sissippi are coal, lumber, crude petroleum (from Louisiana), and 
plantation products such as cotton, sugar, and rice. 

In 1906, the total traffic for the entire Mississippi system, includ 
ing rafts and harbor traffic, amounted to only about 30,000,000 
tons. As in early days, most of the freight moves downstream 

Pacific Rivers of the United States 
The rivers of the United States tributary to the Pacific Ocean 
have a combined navigable length of about 1,600 miles. None of 
them affords navigation far inland (Fig. 305), the San Joaquin and 
Sacramento rivers, especially, being nearly parallel with the coast. 
The Columbia is commercially the most important river of the Pacific 
coast. Ocean steamships reach Portland (some miles up the Willam- 
ette), no miles inland, and river boats go much farther up the 
Columbia and the Willamette, and navigate parts of the Snake, and 
other tributaries. 

As the only river rising east of the Cascade-Sierra Nevada ranges and directly- 
tributary to the Pacific Ocean, the Columbia was the key to political expansion 
on this portion of the coast. The fact that its divergent branches approach closely 
the headwaters of the Saskatchewan and Missouri rivers, along which English 
and American explorers and fur traders advanced, was sufficient to precipitate a 
dispute between Great Britain and the United States for the possession of the 
Oregon country. 

The Colorado River is navigable for light-draft boats in its lower 
course (Fig. 305), but is little used commercially. 

COMMERCE OF THE GREAT LAKES 

General features of the lakes. The Great Lakes constitute 
the most important inland waterways in the world. Their shore- 
line in the United States is more than 2,700 miles long, if measured 
from headland to headland, and more than 4,300 miles, if measured 



USES AND PROBLEMS OF INLAND WATERS 427 

in detail. They are connected by canals with the Atlantic Ocean 
and the Mississippi System (Fig. 318). Unfortunately, the shores 
of the Great Lakes have few naturally good harbors. Several 
of the leading cities and many of the villages on them had their 
locations determined chiefly by the mouths of creeks or rivers. Thus 
Buffalo was located in part by the mouth of Buffalo Creek, Cleve- 
land by the mouth of the Cuyahoga River, and Chicago by the river 
of the same name. The entrances to these and similar streams 
were shallow, and easily choked by drifting sands. As a result, 
harbor improvement has been a frequently recurring problem through- 
out the history of the cities concerned. 

The Great Lakes afford conditions for transportation in many 
ways vastly superior to those of the rivers, and their commerce 
has grown rapidly in spite of railroad competition. At present, 
the principal commodities carried on the Lakes are iron ore, coal, 
lumber, and grain — raw materials of great bulk, and not requiring 
rapid transportation. In 19 10, the total domestic shipments on 
the Great Lakes amounted to more than 86,000,000 net tons, of 
which more than half was iron ore. 

Early navigation. Apart from their use by the Indians, the 
Great Lakes were navigated systematically first by the French fur 
traders from eastern Canada. They discovered Lake Huron first 
(16 1 5), by way of the Ottawa River (Fig. 310), and used the lower 
Great Lakes last, because of the hostility of the Iroquois Indians. 
They navigated the Great Lakes in light canoes which could be 
used also on the streams leading to and from the Lakes, and could 
be carried over the numerous portages. 

The lines which the French used in passing back and forth through the Great 
Lakes region were determined in several cases by the work of glacial waters (com- 
pare Fig. 310 with Fig. 298). Aimost without exception, these lines have con- 
tinued to be of importance in trade and travel. Canals were cut across several 
of the old portages (compare Figs. 310 and 317). Turnpikes and railroads followed 
or paralleled the old lines. A number of villages and cities grew up at strategic 
points where the French had built forts to guard the lines of trade. Between 
Presque Isle (opposite present city of Erie, Fig. 395) and the Allegheny River 
there ran at different times buffalo trail, Indian path, trader's trace, military road, 
turnpike, and railroad. A canal, soon abandoned, also once connected the city 
of Erie with the Ohio River. Long the favorite route of the French between the 
St. Lawrence River and the Great Lakes, the Ottawa Valley was followed by the 
Canadian Pacific Railroad westward from Montreal, and is to be followed by the 
projected Georgian Bay Ship Canal. In connection with the latter, much water 
power will be made available, and the Ottawa Valley probably will become one 



428 



ELEMENTS OF GEOGRAPHY 



of the most important industrial sections of Canada. The above facts illustrate 
the truth of a statement that "trade and civilization in America have followed 
the arteries made by geology." 

The first American sailing vessel appeared on the Great Lakes 
in 1797, but for a time the number increased slowly. In 1812 some 
half-dozen small schooners carried practically all the traffic on Lake 
Erie, and for several years more the business of the upper lakes was 
limited to that of the fur-trading stations. Further development 




Fig. 310. Portages between the Great Lakes and the Mississippi System. 

awaited the introduction of steam navigation, and the settlement 
of the neighboring lake and prairie plains. 

Steam navigation and the settlement of the Great Lakes region. 
Beginning in the decade 1820-1830 there was a large movement of 
population from New England and New York into the Lake region. 
Many causes contributed to it, one of the most important being 
the great reduction in the expense and time involved in reaching 
the Interior, due to the opening of the Erie Canal in 1825 (p. 434), 
and the development of steam navigation on the western Lakes in the 
thirties. The first steamer appeared on Lake Ontario in 18 16, but not 
till ten years later did one enter Lake Michigan, and not until 1832 did 
one visit Chicago. In 1833, there were 11 steamboats on the Great 
Lakes, and by 1848 there were 400 vessels, including 64 steamers. 
Cabin fares on the better boats from Buffalo to Chicago fell from 



USES AND PROBLEMS OF INLAND WATERS 429 




Fig. 311. 



about $25 in 1838, to $6 or $8 in 1852. Steerage fare was consider- 
ably less. It was now possible, furthermore, to take household goods, 
farming implements, and stock into the Interior easily and cheaply. 

A comparison of Figs. 311 
and 312 will show how rapidly 
the northern parts of Ohio, 
Indiana, and Illinois, and the 
southern parts of Michigan and 
Wisconsin were settled between 
1830 and 1850. During this 
period, also, Buffalo, Cleveland, 
Toledo, Milwaukee, and Chi- 
cago experienced their first sub- 
stantial growth. They served 
as points of contact between 
the agricultural Interior and 
the manufacturing and com- 
mercial East. Their prosperity 
depended on commerce; not till 
later did they come to have 
large manufacturing interests. 
Between 1840 and i860 the pop- 
ulation of Chicago increased 
nearly 2 5 fold ; the city changed 
from the 54th in the United 
States to the 8th. 

The "Soo Canal" and the 
opening of Lake Superior. 
Before the "Soo Canal" was 
opened in 1855 there was little 
commerce on Lake Superior, 
and for the most part its shores 
were an unsettled wilderness. 
The canal opened the borders 
of the lake to settlement, and 

permitted the systematic exploitation of their natural resources, 
especially the iron ore (p. 285) and lumber. The value of the canal 
was increased greatly in 1881, when the first enlargement was com- 
pleted. Between 1880 and 1890, the population of the Lake Supe- 
rior counties of Michigan, Wisconsin, and Minnesota increased 




Fig. 312. 

Fig. 311. Distribution of population 
in the Great Lakes region in 1830. 

Fig. 312. Distribution of population 
in the Great Lakes region in 1850. 



43° 



ELEMENTS OF GEOGRAPHY 



respectively 90 per cent, 400 per cent, and 800 per cent. The canal 
contributed greatly to this remarkable growth. In 1896, the canal 
was given a depth of 20 to 21 feet, and a further enlargement is now 
being made. There is also a Canadian canal around St. Mary's Falls. 



Mil. 

. h« «■* i/}\o f-00 O w ci co "* myD r-oo O w <m ro tJ- u-)\o t~o0 O 
°t MKCOMOOOOOCMOOaOO&CJO&OOQOO OOOO O O O M 

Net cooocooooocooooooooooocx>ooocoococccooo aaoo^aooooo 
Tons 




























































A 


60 


























































/ 




58 


























































/ 




56 






























































54 




















































/ 


1 








52 




















































/ 




1 






50 


















































) 


1 










48 


















































/ 












46 


















































/ 












44 


















































( 












42 
























































' 






40 . 
















































1 








5 . 






38 ^ 






























































36 






























































34 






























































32 






























































30 






























































28 






























































26 






























































24 






























































22 






























































20 






























































18 _ 
16 


























































































































14 _ 
12 
























































































































































































8 






























































6 






























































4 






























































2 



























































































































Fig. 313. Diagram 
Canal," 1881-1910. 



showing annual tonnage passing through the " Soo 



In recent years about ^3 of the total traffic of the Great Lakes 
has passed in or out of Lake Superior through the "Soo Canal" 
(Fig. 313). The tonnage passing through it during the seven months 
of the open season is about four times- as great as that passing 



USES AND PROBLEMS OF INLAND WATERS 431 

through the Suez Canal during the entire year. About 4 /s of the 
freight which passes through the "Soo Canal" is east-bound. 

Traffic in iron ore and coal. Fig. 314 shows the location 
of the iron ore fields of the Lake Superior region. In recent years 
they have furnished about 4 /s of the annual output of the United 
States. Fig. 315 shows the movement of iron ore on the Great 




Fig. 314. Map showing the position of the iron-producing areas in the Lake 
Superior region. 1, Michipicoten district; 2, Kamanistquia and Matawin dis- 
trict; 3, Steep Rock Lake and Attikokan district; 4, Vermilion district; 5, Mesabi 
district; 6, Penokee-Gogebic district; 7, 8, and 9, Marquette, Crystal Falls, and 
Menominee districts. 



Lakes. Most of the ore goes to Lake Erie ports, and thence by rail 
to the Pittsburgh region. Most of the iron ore goes to the coal, rather 
than the coal to the iron, because the amount of coal needed in manu- 
facturing steel is greater than the amount of iron ore and because, 
where now manufactured, the steel is nearer its market than it would 
be if manufactured where the iron is mined. As Fig. 315 shows, 
much iron ore also goes to the iron and steel centers near the head 
of Lake Michigan, especially to South Chicago and Gary, Indiana. 
At these points Indiana and Illinois coal (see Fig. 153) may be ob- 
tained cheaply, and they are close to great markets. 



43 2 



ELEMENTS OF GEOGRAPHY 



Many boats which bring iron ore, lumber, and grain to the east- 
ern lake ports take coal back at very low rates. This has helped 
to make possible the recent establishment of the iron and steel 
industry at the western end of Lake Superior. It also means cheap 
coal for domestic and general manufacturing purposes in the region 



VERMILiB^ ' . 




Fig. 315. Map showing movement of iron ore on the Great Lakes in 1909. 
(After Birkinbine.) 



west of Lakes Michigan and Superior, which is without coal resources 
of its own. 

Lumber trade of the Lakes. The western end of the great 
northern forest of pine, spruce, hemlock, cedar, fir, birch, etc., lies 
in Michigan, Wisconsin, and Minnesota (Fig. 428). Lumbering 
operations began in Michigan in the early thirties, and spread west- 
ward and northward. Production increased rapidly after 1850, 
and for many years the Lake states constituted the most important 
lumber district in the United States, furnishing, in 1880, y$ of the 



USES AND PROBLEMS OF INLAND WATERS 433 

total output of the country. Logs cut in the interior were floated 
down the streams to the lakes. At the mouths of the larger rivers 
busy towns developed where the logs were manufactured into lum- 
ber. First from the mill towns of eastern Michigan, and later from 
more distant points, the manufactured lumber was transported at 
low lake rates to Detroit and the cities of Lake Erie. Most of the 
products of the Lake Michigan mills were sent through Chicago to 
the prairies, the settlement of which created a demand for enormous 
quantities of building and fence material. With the depletion of 
the forests of pine near the Lakes and the larger rivers flowing into 
them, mill towns sprang up in the interior, from which more and more 
of the products have been sent to market by all-rail routes. This 
change and the general decline of the lumber industry in the Lake 
region since 1890 (p. 558), due to the cutting away of the forests, 
have reduced greatly the lumber trade of the Great Lakes. In 19 10, 
1,208,000 thousand feet of lumber were transported on the Lakes. 

Movement of grain and flour. The transportation of grain 
and flour has been an important phase of commerce on the Great 
Lakes ever since the settlement of the Lake states. The movement 
is almost entirely from the south end of Lake Michigan and the 
west end of Lake Superior, to the east end of Lake Erie (Why?). 
The railroads are much stronger competitors for the transporta- 
tion of these commodities than for that of iron and coal (Why?). 

Modern lake vessels. Much of the freight on the Great Lakes 
is carried in steel freighters, built for speed, capacity, and strength 
(Fig. 316). Many are 500 to 600 feet long, and have a capacity 
of 10,000 to 12,000 tons. One of the largest carried 13,000 tons of 
soft coal in a single cargo, and on another occasion 422,000 bushels 
of wheat. The latter is said to have represented the production 
of some 30,000 acres. Another lake vessel transported more than 
323,000 tons of iron ore in 27 cargoes during the season of 1907. 

CANALS 

General considerations. The first canal in the United States 
was opened in 1794, but not many of importance were constructed 
until the successful completion of the Erie Canal (1825) aroused 
great interest in canal building. The period of most active canal 
building extended from 1825 to 1837. Altogether, about 4,500 
miles of canals have been constructed in the United States (Fig. 
317). Most of them were designed to extend and supplement 



434 



ELEMENTS OF GEOGRAPHY 



natural waterways. The more important ones were of three classes: 
(i) Those along the Atlantic coast/connecting bays or rivers between 
which the natural water routes involved much greater distances. 

(2) Those connecting, or begun with the intention of connecting, the 
leading Atlantic seaports with the Ohio River or the Great Lakes. 

(3) Those connecting the Great Lakes with the Mississippi System. 
As Fig. 317 shows, many feeders were built for the main canals. 

Of the 4,500 miles of canals constructed, nearly 2,500 miles, 
costing about $80,000,000, have been abandoned. Most of the con- 




Fig. 316. The Coralia loading ore at Escanaba. 
Publishing Co.) 



(Copyright by Detroit 



ditions which contributed to the decline of river navigation (p. 425) 
contributed with even greater force to the decline of the canals. 
They were all shallow, and the canal boats therefore of small capacity; 
many varied in size in their different parts, retarding through traffic. 
The canal boats depended largely on animal towage. Some of the 
canals were located unwisely, some were managed badly, and most 
of them fell an easy prey to railroad competition. Fig. 318 shows 
the canals used more or less in recent years, and Fig. 319 suggests 
the appearance of one of them. 

The Erie Canal. The Erie Canal, connecting the Hudson 
River with Lake Erie at Buffalo (Fig. 317), was built by New York 
to control the trade of the central and western parts of that state, as 



USES AND PROBLEMS OF INLAND WATERS 435 



well as to gain the trade of the Great Lakes region, toward which 

settlement was setting. Much flour, meat, and other products of 

the former sections were going down the Delaware and Susquehanna 

rivers to Philadelphia and Baltimore, and some were seeking the 

Canadian markets along the St. Lawrence River. Such a canal 

was demanded also by military considerations. In the event of 

another war along the 

northern frontier, some 

way better than had 

been available in the 

War of 1812 was 

needed to get supplies 

to the shores of the 

Lakes. 

The canal became 
a great highway of ex- 
pansion into the Inte- 
rior, and a great outlet 
for surplus western 
products; it caused the 
rapid growth of Buf- 
falo, Rochester, and 
other places along its 
course; it increased 
land values throughout 
the region tributary to 
it; and it helped to 
transform New York 
City from a market 

town for the Hudson Valley, into the leading commercial city of the 
country. The cost of transportation between Albany and Buffalo 
fell from $88 to $5.98 a ton in the twenty-six years after the open- 
ing of the canal. The tolls collected on the canal paid for its 
construction in 10 years. 

Until the late 1860's, the Erie Canal was the most important 
transportation route between the Great Lakes and the Atlantic 
Ocean. In i860, 1,500,000 tons of western produce went to tide- 
water by way of the canal, and only 900,000 tons over the four lead- 
ing trans- Appalachian railroads. In 1866, the freight carried by 
the canal was 60 per cent of that moved across New York. Soon 




Fig. 317. Map showing principal canals con- 
structed in the United States. 



436 



ELEMENTS OF GEOGRAPHY 



after this it began to decrease, and the tonnage on the canal has 
been small for years. The people of New York voted in 1903 to 

spend $101,000,000 in im- 
proving the canal, and this 
work is now in progress. 

Canals between Great 
Lakes and Mississippi 
System. It is impractic- 
able to consider here, one 
by one the different canals 
which connected the Great 
Lakes with the Ohio and 
Mississippi rivers (Fig. 
317). In general, they in- 
jured the cities and trade 
of the Mississippi River 
(p. 423), and benefited 
greatly the cities and com- 
merce of the Great Lakes. 
For a time, most of them 
were powerful factors in the 
development of the sections 
which they traversed. In 
addition to bestowing special benefits in different cases, they 
cheapened transportation, opened new markets, raised the prices of 




Fig. 318. Map showing canals actually used 
for purposes of transportation in 1906. (Data 
from map by U. S. Bureau of Corporations.) 




Fig. 319. View on Hennepin Canal, Illinois. 



USES AND PROBLEMS OF INLAND WATERS 437 

farm products, lowered the cost of imported merchandise, increased 
land values, stimulated the growth of population, and helped 
build up towns and cities. The last point may be illustrated in 
the case of Chicago and the Illinois and Michigan Canal, which 
connects the lower Chicago River with the Illinois River (Fig. 317). 
The canal made Chicago the gateway of a large and fertile region 
to the southwest of Lake Michigan. The imports of the city in- 




Fig. 320. Map showing improved waterways of Germany and the Low Coun- 
tries. (After Chisholm.) 



creased from about 2^ millions in 1847 to over 8}4 millions in 
1848, the first year of the canal. The exports increased from a 
little over 2 x /i to nearly 10^4 millions in the same time. The 
canal helped Chicago to become, in the early fifties, the largest 
grain and lumber (p. 433) market in the world. The population of 
the city rose from 16,859 in 1847 to 60,652 in 1853. Some of these 
canals have been abandoned, and for years the rest have been used 
but little. 

Foreign canals. Several foreign countries have systems of 
canals suited to modern conditions of transportation. This is true 
particularly of Germany (Fig. 320). One of the important canals of 
this country (the Kiel Canal) was built to permit ships to pass 



43§ 



ELEMENTS OF GEOGRAPHY 



between the Baltic and North seas without going around Denmark. 
The Manchester Ship Canal (Fig. 321) allows ocean-going ships to 
reach the docks of Manchester from Liverpool. 

IMPROVEMENT OF AMERICAN WATERWAYS 

Why waterways should be improved. It has been apparent 
for some years that the larger rivers of the United States should be 
so improved as to make possible economical transportation upon 




Fig. 321. Scene on the Manchester Ship Canal. 



them. This is desirable because (1) water transportation is nor- 
mally cheaper than rail transportation, and if the cost of trans- 
portation is reduced, the price to the consumer of the commodities 
transported will tend to be lower; (2) waterways tend to keep down 
the rates of competing railroads; and (3) the railroads in recent 
prosperous years have been unable to handle promptly the traffic 
of the country during the busy season. The products and trade of 
large sections of the country are increasing much faster than the 
transportation facilities of the railroads. One of the leading rail- 
road officials of the country estimates that to develop the railroads 
of the United States so that they can handle the traffic of the near 
future would require the expenditure of some $6,000,000,000. The 
Inland Waterways Commission estimated that to develop ade- 



USES AND PROBLEMS OF INLAND WATERS 439 



quately the inland waterways of the country would cost somewhere 
between $500,000,000 and $800,000,000. 

Leading improvements needed. The leading improvements 
advocated by the Inland Waterways Commission are: (1) A deep 
canal (at least 20 feet) between the Hudson River and the Great 
Lakes. The new Erie Canal will 
have a depth of 12 feet. (2) A 
deep inner waterway along the 
Atlantic Coast from New England 
to Georgia (Fig. 322), following 
approximately the line of the old 
"Inland Waterway" (p. 359). (3) 
A deep waterway between Lake 
Michigan and the Gulf of Mexico. 
This involves the extension of the 
Chicago Sanitary and Ship Canal 
(built primarily to dispose of the 
sewage of Chicago) to the head of 
navigation on the Illinois River, and 
the improvement of the Illinois and 
Mississippi rivers. Such a water- 
way would be of great importance 
to the trade between the northern 
and southern parts of the Interior, 
and, following the opening of the 
Panama Canal (p. 533), to the 
trade of the northern Interior with 
the Pacific Coast, and with foreign 
countries both to the south and 
across the Pacific Ocean. (4) A 
canal to connect Puget Sound and 
the Columbia River. 

A canal 25 feet deep is being 
dug across Cape Cod (Fig. 323), 
which will form a link in the At- 
lantic coast improvement. It will shorten the water trip between 
New York and Boston, and will do away with the voyage among 
the dangerous shoals south and east of Cape Cod, where so many 
vessels have been wrecked. 




Fig. 322. Map showing course 
of proposed inner waterway along 
Atlantic Coast, and Hudson River — 
Erie Canal route to Great Lakes. 



44© 



ELEMENTS OF GEOGRAPHY 



MASSA CHUSETTS 



Bost. 





Water Power 

Use in the past in United States. Water power has located many 
manufacturing cities in the United States, and contributed largely 
to their growth. It was used first in a large way in New England, 
where it constitutes one of the leading natural resources. Amoskeag 
Falls, on the Merrimac River, made Manchester; Franklin Falls, 

Nashua, Lowell, and 
Lawrence were located 
by other power sites 
of the same river. A 
number of other New 
England rivers have 
similar importance, in- 
dustrially. Bellows 
Falls, Holyoke, Berlin, 
Biddeford, Lewiston, 
Rumford Falls, Au- 
gusta, and Bath are 
among the busy indus- 
trial centers created 
largely by water power. 
There are many water 
power cities farther 
west. Grand Rapids, 
the second city of 
Michigan and a leading 
furniture manufacturing center, is an example. Located 40 miles 
inland at the rapids of the Grand River, its first lumber mills were 
at a disadvantage compared with those on the shores of the Lakes 
(p. 433; Why?). As a result, cabinet shops and furniture factories 
were soon established. (What was gained by doing this?) The 
power afforded by the river was soon outgrown, and the timber sup- 
ply in the vicinity exhausted, but the advantages of an early start, 
and of established plants with world-wide reputations for furniture of 
superior quality, keep the city to the front. Similarly, St. Anthony's 
Falls and command of the forests and wheat-fields of Minnesota made 
Minneapolis an important manufacturing city. The settlement of 
the Red River Valley began in the middle seventies (p. 402), and in 
1876 Congress provided for the construction of a wall behind these 



iFall River MJ 



NANTUCKET - 
SOUND i I 




Fig. 323. Map showing canal across Cape Cod. 



USES AND PROBLEMS OF INLAND WATERS 441 

falls, to prevent erosion and increase the discharge of water. In 1881, 
the improved power operated 28 flouring mills with a yearly capacity 
of more than 20,000,000 bushels of wheat, representing the product 
of 1,250,000 acres. The falls also furnished power to 17 lumber 
mills. The population of Minneapolis increased from less than 
47,000 in 18S0 to nearly 165,000 in 1890. In 1905, the value of the 
flour and grist mill products of Minneapolis was about 9 per cent 
of the total for the United States. 

Water power formerly had certain disadvantages, because the 
mills using it had to be located close to the source of the power. 
Coal was abundant and cheap, and was used more and more 
for manufacturing purposes. In 1870, streams furnished 70 per 
cent of the total power used in New England, 50 per cent of that 
used in the Middle Atlantic States, and 49 per cent of that in the 
South Atlantic States. Thirty years later, these percentages had 
fallen to 35, 14, and 11. Water power continued to be used most in 
connection with long-established industries. It also continued to 
be used largely in connection with certain industries presenting special 
conditions, such as the paper and pulp industry. Beside an abun- 
dance of clear water, this industry is favored by nearness to (1) 
forests affording the raw material, and (2) markets. Its leading 
centers are in New England, the Adirondack region of New York, 
and the lower Fox Valley in Wisconsin. 

Present conditions and future importance. During recent 
years there has been a great increase in the use of water power in 
the United States. In 1900, 1,454,229 horse power were developed 
from water, and in 1908, 5,356,680 horse power. This change has 
been due largely to the following conditions, which also will help 
to bring about an increasing use of water power in the future: (1) 
There have been rapid developments in the transmission of energy in 
the form of electricity. Electric power developed by4alls_aiid~rapids 
(hydro-electric power) is transmitted some 220 miles in California, 
300 miles by a Colorado company, and 500 miles in Italy. On the 
basis of a radius of transmission of 200 miles, a water power could, 
if sufficient, serve an area of 125,000 square miles. In the future, 
few places in the United States will be beyond the reach of hydro- 
electric power. Power from Niagara Falls now runs street cars, 
lights buildings, and is furnished very cheaply for industrial pur- 
poses in Buffalo and other cities as far away as Utica. On the 
Canadian side, it is carried to various cities and villages as far away 



442 ELEMENTS OF GEOGRAPHY 

as the Detroit River. Snoqualmie Falls, Washington, furnish power 
for electric lights, street railways, motors, etc., in Seattle and Ta- 
coma, some 50 miles distant. (2) In some ways, electric energy 
is superior to other kinds for large plants, and it also has a great 
advantage over other forms of power in its capacity for subdivision, 
so that it may be carried economically to the small user. (3) In 
many places, hydro-electric power is even now cheaper than power 
obtained from coal. 

About 26,000,000 horse power are developed now from coal in the United 
States. It is estimated that of this amount some 15,000,000 horse power could be 
developed by water with an average saving of $12 per annum per horse power, 
or a total saving of $180,000,000. In addition to the $180,000,000 gained by the 
substitution, there would be saved each year about 150,000,000 tons of coal. This 
is about one-third the coal mined in the United States, so that the substitution 
would lengthen greatly the duration of the coal supply (p. 281). 

As the supply of coal diminishes and its cost increases, electricity 
developed by water will be used more and more for transportation, 
lighting purposes, and manufacturing. Certain railroads already 
have acquired water power sites in the western mountains, with a 
view to moving their trains over the mountains by hydro-electric 
power. Doubtless the time is not distant when most railroads, 
street cars, and inter-urban lines will be operated in this way. Ulti- 
mately, nearly all manufacturing industries will depend largely on 
water power, and it is fortunate indeed for the future of the United 
States that no other nation has more available water power. 

Amount and distribution of water power in the United States. 
In view of the part which water power is to play in the life of the 
nation, its amount and distribution are matters of great interest 
and importance. The total amount has been estimated on several 
bases. « (1) If the amount of water available in the streams during 
the two weeks of lowest water were used throughout the year, and 
all above that amount escaped unused, about 37,000,000 horse 
power could be developed. This is called the primary horse power. 
(2) If plants were established to develop the minimum power avail- 
able for the six high-water months, there would be about 66,500,000 
horse power per year. (3) If the flood waters were stored in reser- 
voirs, so that the streams were utilized fully, there could be developed 
between 100,000,000 and 200,000,000 horse power. The significance 
of these figures is realized best when it is remembered that now 
about 26,000,000 horse power are developed from coal, and only 



■: 



USES AND PROBLEMS OF INLAND WATERS 443 

about 5,500,000 from water. The estimated distribution of water 
power throughout the country on the first two bases given above 
is shown in the accompanying table. 



TABLE SHOWING ESTIMATE OF STREAM FLOW AND WATER 
POWER IN THE UNITED STATES 



Principal Drainages 



Northern Atlantic to Cape Henry, 
Va 

Southern Atlantic to Cape Sable, 
Fla 

Eastern Gulf of Mexico to Mis- 
sissippi River 

Western Gulf of Mexico west of 
Vermilion River 

Mississippi River, main stream . . 

Mississippi River tributaries 
from east 

Mississippi River tributaries from 
west, including Vermilion 
River 

St. Lawrence River to Canadian 
Line 

Colorado River, above Yuma, 
Ariz 

Southern Pacific to Point Bonita, 
Cal 

Northern Pacific 

Great Basin * 

Hudson Bay 

Total 



Drainage 
Area. 



Sq. Mi 



159,879 

123,920 

142,220 

433.700 
1,238,800 

333,600 

905,200 
299,720 
225,000 

70,700 
290,400 
223,000 

62,150 



4,508,2^ 



Flow Per 
Annum. 

Billion 
Cu. Ft. 



8,942 
S,S6o 
6,867 

2,232 

21,940 

12,360 

9,58o 

8,583 

521 

2,193 
15,220 

614 



94,612 



Horse Power Available 



Primary or 
Minimum 



1,702,000 
1,253,000 

559,°oo 

433,760 

147,000 

2,472,590 

3,948,970 
6,682,480 

2,918,500 

3,215,400 

12,979,700 
518,000 

75,800 



36,906,200 



Minimum of 
the Six 
Highest 
Months 



3,186,600 

1,957,800 

963,000 

822,650 
335,000 

4,940,300 

7,085,000 

8,090,060 

5,546,000 

7,808,300 

24,701,000 

801,000 

212,600 



66,449,310 



Control of water power in the United States. In the future 
the control of the water powers of the United States will also mean, 
to a large extent, the control of the industries of the country. It 
is clearly desirable that the water powers be developed under con- 
ditions that will protect the public from monopoly and extortion, 
and that will, at the same time, afford a full, reasonable return on 
the capital invested in developing them. All navigable streams are 
under the control of Congress, both as regards navigation and their 



444 ELEMENTS OF GEOGRAPHY 

use for power purposes. Non-navigable streams belong to the states. 
In the past, many valuable water power privileges have been granted 
to companies forever, without adequate return to the public (the 
original owner) or provision for its protection. It seems likely 
that hereafter, in most cases, ownership will remain with the nation 
or state, as the case may be, and that leases for definite periods 
will be granted to hydro-electric companies, permitting water power 
to be developed under conditions safeguarding the interests of the 
public. Many power sites in the Public Domain have been withdrawn 
from private entry, to await action by Congress concerning their 
use or disposal. More than 1,500,000 acres in 12 states, now (June, 
191 1 ) stand withdrawn. 

Improving water powers. It is highly desirable that power 
streams should maintain a relatively even flow. If a stream can 
develop 5,000 horse power during brief flood stages, and only 500 
horse power the rest of the time, not much more than the latter 
amount can be used, and the rest is lost. Protective forests about 
the headwaters of mountain streams and systems of reservoirs to 
hold storm-waters are therefore important to manufacturing inter- 
ests, as well as to navigation and farming (pp. 267-269, 342). 

Water power in other countries. Water power is afforded 
by most large streams in mountainous regions, and by many youth- 
ful streams in non-mountainous regions, especially those that have 
been glaciated recently. In Europe, Switzerland is likely to be the 
first country to utilize fully its water power resources (p. 383). The 
streams of Scandinavia, Austria-Hungary, France, Italy, and Germany 
also afford much power. Enormous power could be developed from 
the streams of the Caucasus and Himalaya mountains, but this 
is not likely to be done in the near future. Considerable power 
may be obtained from the streams of eastern Australia. Canada 
has an abundance of water power, both in the western mountains 
and in the eastern part of the country. In the latter section, it is 
due largely to glaciation. Many other countries have more or 
less water power, much of which will be of value to man sometime, 
if not so now. 

Switzerland, Italy, the province of Ontario in Canada, and 
the provinces of New South Wales and Victoria in Australia are 
among the countries that have made much greater progress than 
the United States toward solving the difficult problems of the con- 
trol of water power. 



USES AND PROBLEMS OF INLAND WATERS 445 

Irrigation 

Irrigation means the artificial application of water to land for 
the benefit of plants. It is practiced in many dry regions because 
otherwise crops cannot be grown, and it is being introduced more 
and more into humid regions, in order to increase the yield of crops. 
Even in eastern United States, there is scarcely a year when some 
crops do not suffer from lack of rain, and there are occasional years 
of serious droughts. 

The familiar statement that agriculture without irrigation can- 
not be carried on successfully where the annual rainfall is less than 
twenty inches is very misleading. The development of "dry farm- 
ing" (p. 498) and the introduction of drought-resisting plants (p. 276) 
are changing some semi-arid regions into fairly productive farm lands, 
without irrigation. Again, much depends on the distribution of the 
rainfall. If it came just when the plants needed it, ten or twelve inches 
would suffice to grow many staple crops by ordinary methods of 
farming. The yields that would be obtained under such conditions 
could be increased greatly, however, by irrigation. 

Practiced since ancient times. Irrigation was practiced in 
Egypt 2,000 years before Christ, and probably much earlier. For- 
merly, the extent of the irrigable area was determined directly by 
the height to which the Nile rose. The great Assuan dam, at the 
first cataract of the Nile, now controls the river, and increases greatly 
the area which may be watered. About 6,000,000 acres have been 
irrigated in Egypt in recently ears. 

The ancient civilizations which existed in Mesopotamia were 
made possible by extensive systems of irrigation. The ditches of 
the region have long been unused, and much land which once was 
cultivated is now waste. The English government has extended 
irrigation in India until about 50,000,000 acres are so watered 
(Fig. 324), an area larger than that irrigated in any other country. 

IRRIGATION IN WESTERN UNITED STATES 

Irrigation was practiced first in the United States in Arizona 
and New Mexico. In the latter, there are ditches said to have 
been used continuously for 300 years by people of mixed Span- 
ish and Indian descent. The Mormons were the first Americans 
(except Indians) to irrigate systematically. The conditions for 
irrigation were ideal on the slopes of alluvium at the base of 



446 



ELEMENTS OF GEOGRAPHY 



the Wasatch Mountains, and without irrigation they could not 
have been cultivated. Irrigation by Americans in the Salt River 




Fig. 324. Map showing principal irrigation systems of India. 

Valley of Arizona began in 1867, and in southern California a few 
years later. 

Value of irrigated land. Irrigation transforms unproductive, 
worthless, or nearly worthless, land, into land producing more than 



USES AND PROBLEMS OF INLAND WATERS 447 







Fig. 325. The Yakima desert before irrigation. Near North Yakima, 
Washington. (U. S. Reclamation Service.) 




Fig. 326. The region shown in Fig. 325, after irrigation. (U. S. Reclama- 
tion Service.) 



448 



ELEMENTS OF GEOGRAPHY 



the average farm land in eastern United States. (Compare Figs. 
325, 326, and 327.) Irrigated lands are worth from $100 or $150 
an acre for general farming purposes to $2,000 or more an acre for 
choice fruit lands with good orchards. In general, the great value 
of much of the irrigated land is due to the following: (1) The soil 
of arid regions is likely to be rich in mineral plant foods, because 
for ages ground-waters have come to the surface through capillary 



























11 liM ii»iiiifflll nil 








f k^; 


i^JS Bn| 






aSr "' "«H : 








1 ' ■■*•'■ i- *i 


..,;-*' wJHj 














'fc.lR- ;. 


■ -"" US 






^fc^. - l,lil l 








!§t 






^^^vWi 


-■ 


>" "^ >u 




1 



Fig. 327. A vineyard near North Yakima, Washington. (U. S. Reclamation 
Service.) 



action, and as they evaporated into the dry air they have deposited 
in the soil the mineral matter dissolved during their journey under 
ground (p. 332). In some cases when irrigating waters have been 
turned on the land it has been found that certain materials (alkaline 
salts) had accumulated in this way to such an extent that plants 
would not thrive until the soil was partially leached out. (2) Irri- 
gated soils, when used rightly, are durable. Soil wash can be avoided 
largely, and there is a large store of soluble mineral matter in the 
sub-soil. (3) Irrigating waters contain fertilizing matter in solution, 
which is immediately available to the roots of the plants. (4) Irri- 
gated crops, if properly cared for, get just the amount of water needed 
at just the time they need it. (5) In the warmer sections of the 
West, several crops a year may be grown. In the Imperial Valley, 
for example, six crops of alfalfa can be grown each year. 



USES AND PROBLEMS OF INLAND WATERS 449 



Area of irrigable land. As the demand for land increases 
with the population, it will be advisable to extend irrigation to the 
utmost limit. The question as to how much land can be irrigated 
is therefore a vital one. In 1890, irrigation experts estimated that 
some 100,000,000 acres in the arid West might be reclaimed in this 
way. Later, the estimates 
were reduced to 60,000,000 
acres, and now only about 
45,000,000 acres (an area 
the size of Missouri) are 
thought to be irrigable. 
In other words, the 
Government Reclamation 
Service expects that only 
about 5 per cent of the 
entire arid region can be 
won to agriculture in this 
way. The chief factors 
which will control the area 
are matters of topography 
and rainfall. (1) The 
water supply comes largely 
from rain and snow falling 
on the mountains, and the 
mountain catchment areas 
are comparatively small. 
Furthermore, only a small 
fraction of the rainfall of 
the arid region can be 
made available for irriga- 
tion (Why?). (2) The volume of many of the western rivers varies 
greatly (Why? Fig. 328), and in many cases it is necessary to build 
dams to hold the flood waters in reservoirs, so that they may be 
let out as needed during the growing season. Most of the larger 
government dams are built in narrow places in canyons (Fig. 334). 
Unfortunately, there are comparatively few places suited for storage 
of large amounts of water, and in some cases where there are good 
sites for dams, the tributary catchment areas furnish little water. 
(3) In many places the ground is too rough to make the distribution 
of water on it practicable. (4) In many localities the possible crops 



|5,S 


Jan. Feb. Mar. Apr. Mav Jun. Jul. Aug. Sep. Oct. Nov. Dec. 






















6 














18 


95 






4 






















2 








































4l) 
























W 
























M 
























TO 
























26 
























?.?. 
























18 
























14 










1 






18 


96 






10 










1 


I 












8 










1 














6 






[ 


, 


l 1 












4 






| 


Aj 


l 














2 






J 


m 














u 


mM 


fatf 


td 










1 It 


^ 



Fig. 328. Diagram showing discharge of 
the Boise River above Boise, Idaho, in 1895 
and 1896. (Newell, U. S. Geol. Surv.) 



45° 



ELEMENTS OF GEOGRAPHY 



probably would not justify the necessary expense of getting the 
water on the land. (5) The area which can be irrigated depends in 
part upon the amount of water per acre required for crops. In the 
case of the government projects (p. 452), this varies from i}4 to sH 
acre-feet per year. (Apart from the fact that some crops require 
more water than others, why should the variation be so great? 

Why has it been neces- 
sary to provide nearly 
four times as much 
water per acre on the 
Yuma Project [Fig. 331] 
as on the Milk River 
Project?) 

There are several 
reasons for hoping that 
the irrigable areas may 
prove larger than indi- 
cated above. (1) Many 
fields are now poorly 
prepared for the water, 
so that it spreads 
unevenly, and more is 
required than would be 
if the land were less un- 
even. With the land 
better prepared, the 
water could be spread over a larger area. (2) Much more land 
could be watered if loss by seepage from the canals were not so 
great. This now amounts, on the average, to about 25 per cent 
of the water, and, as the value of the latter increases, the loss 
probably will be reduced more and more by lining the canals with 
cement (Fig. 329). (3) The loss of water by evaporation from the 
canals also will be reduced. (In what ways does the planting of 
trees along the banks [Fig. 330] help to do this? In what parts 
of the West would this be most helpful?) (4) Many irrigators now 
use much more water than is necessary to secure the largest returns. 
This will be corrected by legislation, and by increasing intelligence 
on the part of the farmers. (5) Measurements to determine the 
amount of available water have been made on only a part of the west- 
ern streams, and on most of these the readings cover only a few years. 




Fig. 329. A canal lined with cement. Truckee- 
Carson Project, Nevada. (U. S. Reclamation 
Service.) 



USES AND PROBLEMS OF INLAND WATERS 451 



Further work along this line may indicate that the streams can 
furnish more water than is now supposed. (6) Detailed topographic 
surveys have not been made for much of the West, and they may 
add new possibilities. 

Government projects. Irrigation was begun in the West by 
individual settlers, who took up homesteads and led water to their 
fields from small 
rivers and creeks. In 
1877 Congress sought 
to stimulate indi- 
vidual endeavor by 
legislation, but co- 
operation was neces- 
sary before extensive 
areas could be wa- 
tered. This has been 
brought about in 
various ways. Many 
so-called ' ' irrigation 
districts" have been 
organized to reclaim 
land under state laws. 
Since 1894, much land 
has been reclaimed, 
especially in Idaho 
and Wyoming, under 
the Carey Act, which 

provides for irrigation through co-operation by the nation, state, 
corporations, and settlers. While much was being accomplished in 
these ways, it became evident that the federal government must itself 
undertake those projects that were too expensive, too large, or too 
slow in producing returns, to tempt individuals or corporations. 
Hence Congress passed the National Reclamation Act in 1902. This 
act provides that money derived from the sale of public lands in 
the arid states shall constitute a reclamation fund. The cost of 
any given project is assessed against the land benefited, and is paid 
by the settlers in ten equal annual payments. The moneys returned 
to the government, together with the proceeds of the sale of other 
lands, are used again for further reclamation. 

There are some thirty government projects under way (Fig. 331), 




Fig. 330. An irrigating canal in the Salt River 
Valley, Arizona. 



45 2 



ELEMENTS OF GEOGRAPHY 



which, when finished, will irrigate more than 3,000,000 acres. The 
average cost to the settler probably will be $40.00 to $50.00 per 
irrigated acre. The successful prosecution of these great pro- 
jects by the government has greatly stimulated private enterprise. 
It is impracticable to describe the several government projects 




Fig. 331. Map showing Government irrigation projects. 



here, but a few facts concerning some of them will illustrate the 
scope of the work. The Salt River Project (Arizona) has the 
recently completed Roosevelt dam, 280 feet high (Fig. 332). This 
dam forms a lake covering 16,320 acres. The water power developed 
by the issuing water is used to pump ground-water to irrigate more 
land, for lighting purposes, and in other ways. The storage dam 
for the Rio Grande Project is one of the largest in the world. It 
will make a lake 40 miles long, covering 40,000 acres, and contain- 
ing 2,600,000 acre-feet of water, or nearly two and one-half times the 
amount in the reservoir produced by the great Assuan dam on the 
Nile River. The water for the Truckee-Carson Project (Nevada) 



USES AND PROBLEMS OF INLAND WATERS 453 

is stored in Lake Tahoe, a glacial lake in the Sierra Nevada Moun- 
tains. From Truckee River, the outlet of the lake, it is diverted 
into a canal and carried across to the Carson Valley to reclaim land 
which, in its natural condition (Fig. 333), was composed largely of 
sand dunes and alkali flats. Nearly half the area of the Klamath 



m 






.?: '-■'■ ^ _■ '" : ; 








M 

1 i tej! 


Nk- 














- 1^ ; 13 


K;/ .""■ 


^s 


■5? 


1 '- - iWII«Hf 



Fig. 332. Roosevelt dam, Salt River Irrigation Project, Arizona. 280 feet 
high; 235 feet long on bottom; 1080 feet long on top. Capacity of reservoir, 
1,284,000 acre-feet. (U. S. Reclamation Service.) 



Project (California-Oregon) is occupied by swamps and lakes, so 
that it must be drained before it can be irrigated. The water 
supply for the Shoshone Project, in northern Wyoming, is derived 
from the Shoshone River. To regulate the discharge of this river, 
the government has built a dam 328^ feet in height (Fig. 334), the 
highest structure of the kind ever built. 

Crops of the irrigated lands. The soils of the irrigated lands 
range from heavy clay to light sand. In altitude, they occur from 
below sea-level up to elevations of 6,000 and more feet, and in lati- 
tude, from the Mexican to the Canadian boundary. Winter tem- 
peratures fall far below o° F. in some of the regions concerned, and 



454 



ELEMENTS OF GEOGRAPHY 



the summer temperature reaches 120 F. in the region of the Salt 
River Project. In response to these and other variations, many 




Fig- 333. Land in the Truckee-Carson Project before irrigation. 



different crops are grown on the irrigated lands. Alfalfa and sugar 
beets are produced in many places. Hay, grain, and vegetables 

are staple products in 
Montana and Wyom- 
ing. In addition to 
these things, fruits are 
grown extensively in 
Idaho, Washington, 
Oregon, and Colorado. 
The great citru9 fruit 
region is in southern 
California, and the 
business has grown 
rapidly, especially 
since the middle nine- 
ties. In the season of 
l8 94-5> 5,575 carloads 
of oranges and lemons 
were shipped from the state. In ten years this increased to 31,422 
carloads, or more than 10,000,000 boxes, valued in California at about 




Fig- 334- 
shone River. 



Site of the great dam on the Sho- 



USES AND PROBLEMS OF INLAND WATERS 455 

$27,000,000. In 1909-10, more than 16,000,000 boxes were shipped. 
The growing of deciduous fruits (peaches, pears, and the like) 
also has become of great importance in California, as in various 
other sections of the West. The shipping of these fruits in large 
quantities to distant markets has been made possible by the 
development of the refrigerator car, in which more than 90 per 
cent of the shipments from California are made. In the extreme 
southwest, the leading products are semi-tropical fruits, cereals, 
and alfalfa. 

Population capacity of the irrigated lands. The high value 
of the irrigated lands encourages methods of tillage which secure 
maximum yields from minimum areas, and, together with the diffi- 
culty of hiring effective labor in the West, leads to small farms. In 
orchard regions, 5 to 10 acre holdings are common. The farm unit 
on the government projects is fixed by the Secretary of the Interior, 
and is based upon the amount of land needed to support, in comfort, 
an average family. On a number of the projects, the unit has been 
fixed at forty acres. These things mean a dense rural population. 
The Chief of the Reclamation Service believes that the ultimate 
population of the irrigated lands probably will not be far from one 
person to an acre. 

Farm villages. In many ways, social conditions promise 
to be 'nearly ideal in most of the irrigated districts. The small 
farm units will make it possible for many of the farmers to live in 
town, going to and from their land daily. It seems probable that 
each 5,000 or 6,000 acres of cultivated land will support a farm 
village, where the farmers will have the advantage of graded schools, 
public libraries, etc. On a number of the government projects, 
the Reclamation Service has laid out town sites about six miles 
apart (Fig/335), and set aside lots for churches, schools, and ceme- 
teries. The town lots are sold to the highest bidders, the proceeds 
going to the Reclamation Fund. Irrigation promises to create 
many small villages, rather than a few large cities. 

Irrigation and the National Forests. It is highly important 
from the standpoint of irrigation, as of navigation and water power, 
that the flow of the streams be uniform. The preservation of forests 
about the headwaters of the streams helps to bring about a more 
even flow of water, and partly for this reason the National Forests 
have been established (Fig. 336). Outside Alaska, these forest 
reserves have an area (August, 191 1) of 144,000,000 acres. They 



456 



ELEMENTS OF GEOGRAPHY 



are cared for according to the principles of scientific forestry by the 
Forestry Bureau of the Department of Agriculture. 

IRRIGATION IN THE HUMID STATES 

Future importance. It has been estimated that the yield 
of every important crop of eastern United States could be doubled 
by irrigation. It is therefore certain to be practiced more and more 




Fig- 335- Plan for village on Government irrigation project. (U. S. Recla- 
mation Service.) 

in the future, as the population increases and the demand for food 
grows. As in the West, the irrigator can apply just the amount of 
water needed at just the time required, and he can grow many more 



USES AND PROBLEMS OF INLAND WATERS 457 




fa 




458 ELEMENTS OF GEOGRAPHY 

plants on an acre than otherwise. (What would limit the closeness 
of stand, under irrigation?) 

Present situation. Irrigation is practiced in some of the humid 
states in growing certain crops. For example, water is pumped 
from wells on to the land at various points on the coastal plain 
between New Jersey and Florida, to irrigate truck farms. In the 
latter state, irrigation has been undertaken recently on a rather 
large scale. This is particularly interesting, since all parts of Florida 
receive more than 50 inches of rain a year, and some parts more 
than 60 inches. But much of the soil does not retain moisture well, 
evaporation is great, and the fruit groves and truck farms are bene- 
fited by watering during the drier season. Their products are so 
valuable that even a partial crop failure means heavy losses. Recent 
progress in irrigation in Florida dates from the two great frosts of the 
winter of 1894-95, when many orange groves were destroyed. Some 
of the fruit growers then engaged in truck farming by irrigation, and 
met with such success that the practice has spread rapidly. Much 
of the land in Florida has to be drained before it can be irrigated, for 
half the state is swamp land. Irrigation is practiced extensively 
on the rice-fields of Louisiana, Texas, and the Carolinas. 

As yet, irrigation in the East is restricted largely to special crops 
which warrant relatively large expenditures, such as strawberries, 
raspberries, blackberries and other fruits, and certain vegetables. 
With these crops, a small or imperfect yield because of drought is 
disastrous. 



Reclamation of Swamp and Overflowed Lands 
wet lands of the united states 

The reclamation of swamp and lake areas has been referred to 
incidentally in other connections (pp. 272-273, 372, 375, 400). The 
matter is summarized briefly here. 

Area, distribution, and ownership. The Department of Agri- 
culture estimates that the total area of swamp land in the United 
States is about 79,000,000 acres. It is estimated also by some 
that about 77,000,000 acres can be reclaimed ultimately. Swamp 
lands occur in many states, but the largest areas are in the states 
containing (1) the Atlantic and Gulf coastal plains, (2) the flood- 
plains of the Mississippi River and its larger tributaries, and (3) 
the area covered by the last ice-sheet. Among the states having 



USES AND PROBLEMS OF INLAND WATERS 459 

large areas of swamp land are Florida, with 18,560,000 acres; Louisi- 
ana, with 9,600,000; Mississippi, with 6,173,000; and Arkansas, with 
5,760,000. 

In 1849 and 1850 the federal government granted nearly all 
the public swamp lands to the states. More than Vioof these lands 
are now in private hands. 

Status and cost of reclamation. It is estimated that nearly 
16,000,000 acres have been drained, mostly in the northern interior 
states. In most other parts of the United States, the problem of 
draining wet lands received little attention until the last few years. 
This was due to the abundance, till recently, of good land not 
requiring drainage. Progress is now being made in Florida (p. 458), 
Louisiana (p. 273), and other states. 

The cost of reclamation varies with the character of the swamp, 
the methods employed, and the machinery used, from $3 or so an 
acre, to $30 or more. In some cases ditches only are needed, and 
the cost is then slight; in other cases tile-draining is necessary, and 
then the cost depends largely on the character of the land. Along 
many rivers and coasts it is necessary to build dikes. The water 
of the swamps is then brought to certain points by drains or ditches, 
and pumped out over the dikes. In many such cases, rather large 
areas are treated as units, and improvements in methods and machin- 
ery have reduced the cost one-half in the last 15 years. The esti- 
mated cost of reclaiming 91,000 acres of Wabash River bottom lands 
is $8.00 an acre. In southeastern Missouri 500,000 acres can be 
reclaimed for about $10.00 an acre. The average cost per acre of 
draining the wet lands is much less than that of irrigating the dry 
lands (p. 452). 

Results of reclamation. (1) The soils of most reclaimed 
swamp lands are clayey (Why?). In many cases they are "sour" 
and "cold" at first, but lose these characteristics under proper 
tillage. As a class, they are very fertile (Why?). Since most 
swamp areas are of little use, it is clear that drainage greatly increases 
land values. 

The value of drained farming land varies from $20 or less an acre, to $500 
and more. It depends largely on the character of the soil, the climate, transpor- 
tation facilities, nearness to or distance from good markets, etc. It has been 
estimated that the 77,000,000 acres of swamp lands in the United States which 
probably can be reclaimed will have an average value of $60.00 an acre — a total 
value of $4,620,000,000. Their present value has been estimated at $8.00 an 
acre, and the average cost of draining at $15.00 an acre (perhaps too low) — making 



460 ELEMENTS OF GEOGRAPHY 

a total of $1,771,000,000. According to this estimate, the increase in land values 
through drainage therefore would be $2,849,000,000. Obviously, these figures 
have no exact value, and serve only to give a general impression of the enormous 
future value of the wet lands. 

(2) The products of the drained lands will increase greatly the 
crops of the country, and will feed and support millions of people. 

Perhaps 50,000,000 acres of the present swamp lands will support a family 
to each ten acres, under the conditions likely to prevail in the United States a 
century or two hence. This would mean 5,000,000 families, and, assuming 5 
persons to a family, 25,000,000 people. If the remaining 27,000,000 acres were to 
average one family to 50 acres, they would support 540,000 families, or 2,700,000 
people. This added to the 25,000,000, would give 27,700,000. It is assumed 
in most estimates that the urban population dependent indirectly en the lands 
in question will equal the rural population. On this assumption, the total popu- 
lation of the present swamp regions would become 55,400,000. Probably this 
is putting the urban population too high. If it be taken at % the rural population, 
the total would be 48,475,000. These considerations serve at least to show the 
truth of an earlier statement (p. 372) to the effect that the wet lands constitute 
one of the greater natural resources of the nation. 

(3) An immediate effect of the systematic draining of the swamp 
lands will be to increase the healthfulness of the areas concerned. 
The principal breeding places of malaria-carrying mosquitoes will 
be destroyed, and that disease practically stamped out. The present 
annual loss to the country from malaria, due to the reduced efficiency 
of the sufferers, the losses to business in areas affected, etc., has been 
estimated at $100,000,000. 

Men competent to judge have declared that the economic development of 
much of New Jersey has been retarded by the mosquito plague. Many places in 
the state have been prevented in this way from becoming residence suburbs, 
manufacturing centers, or summer resorts. In some localities in the southern 
part of the state, repeated attempts have been made to carry on the dairy industry 
for the nearby city markets, but in most of these cases the attacks of swarms of 
mosquitoes have so reduced the yield of milk that the business was abandoned. 
A few years ago the Legislature of New Jersey appropriated $350,000 for ditching 
and filling coastal marshes. The mosquito has been exterminated largely in the 
areas where the work has been done, and the state probably will be freed from the 
pest within a few years. 

Reclamation of lake-covered lands. Lakes merge into swamps, 
and many so-called lakes doubtless are included in the estimate of 
swamp areas already given. Ultimately, most shallow ponds and 
lakes will be drained. It will always be impracticable to drain some 
lakes, and many others will be carefully protected and preserved 
(P- 403). 



USES AND PROBLEMS OF INLAND WATERS 461 



WET LANDS OF OTHER COUNTRIES 

Large areas of wet land have been reclaimed in Europe. Much 
land now farmed in Holland was won from the sea. About yi of 
England was marsh or bog land in the reign of Alfred the Great (871- 
901). Probably "not far fromVaoof the tillable land in Europe was 
inundated and unfit for agriculture in the eighth century of our era." 

Vast areas of swamp land in various tropical countries probably 
will remain in their present condition for a long time. 

Water Supply 

Apart from its support of plant and animal life, the most impor- 
tant use of water is for domestic and municipal purposes — for 
drinking, bathing, and various household purposes, for sprinkling 
streets, flushing sewers, for fire protection, manufacturing, and the 
like. It is estimated that between 50 and 150 gallons of water per 
person are used daily in the cities of the United States. Of this, 
about half a gallon per person is used for drinking. 

Sources of water supply. (1) Rain-water, stored in cisterns 
and "tanks," is used extensively for drinking in the arid states, 
and for other purposes throughout the country in rural communities 
and villages. (2) Most of the rural population of the United States 
obtains water for domestic purposes from underground, through 
ordinary wells and springs; but no large city could get sufficient 
water in this way. Thousands of wells and springs have failed 
in recent years because the water table (p. 321) has been lowered 
by unwise farming and deforestation (p. 325). (3) In the Atlantic 
Coastal Plain, the Great Plains, and some other parts of the country 
where the arrangement and position of the rock strata are favorable, 
artesian wells (p. 326) supply large amounts of water. 

Sand and gravel are in general good water bearers, while clay yields relatively 
little water (Why?). Many wells sunk in the glacial clays of northern United 
States obtain their water chiefly from associated beds or pockets of sand and 
gravel. Among the solid rocks, sandstone is a good water carrier, because it is 
porous, and shale a poor one, because it is compact. Most of the igneous and 
metamorphic rocks are dense, and hold little water, the largest supplies being 
found in cracks and other openings in the rocks. 

(4) Thousands of lakes, particularly in the glaciated parts of the 
country, may serve as sources of water supply for neighboring cities 
and villages, and many are so used now. From the Great Lakes or 



462 ELEMENTS OF GEOGRAPHY 

their connecting rivers, Buffalo, Cleveland, Detroit, Milwaukee, 
Chicago, Duluth, and many smaller cities obtain their supply of 
water. (5) Many villages and cities draw their water supply from 
streams. Thus New York City obtains its supply from streams 
and reservoirs in the Catskill Mountains and the uplands east of 
the lower Hudson River; Philadelphia depends on the Delaware 
and Schuylkill rivers, Cincinnati on the Ohio, Minneapolis and St. 
Louis on the Mississippi, and Omaha and Kansas City on the Mis- 
souri. 

In recent years various cities have outgrown their supplies of water and have 
had to seek new supplies, in some cases at considerable distances and at great 
expense. Los Angeles is expending more than $25,000,000 in this way. Water 
is to be brought from Owens River, across the Mojave Desert and through the San 
Bernardino Mountains, in an aqueduct of steel and concrete some 240 miles 
long. Great reservoirs are being built, one of the dams of which is 140 feet high. 
The daily capacity of the system will be about 258,000,000 gallons. New York 
City is expending nearly $100,000,000 to obtain an additional supply of 500,000,000 
gallons a day from the Catskill Mountains, more than 80 miles away. 

Quality of waters. Drinking water should be reasonably 
clear, tasteless, and free from germs of disease. Some cities have 
expended large sums to guard the purity of their water supplies. 
Some of them have bought large tracts of land, with their lakes, 
springs, and other stream sources. The waters of these tracts 
are then protected carefully from contamination, and carried to 
cities in ways that prevent pollution on the way. Other cities have 
established filtering plants through which all the city water passes 
before use. Nevertheless, the use of impure drinking water is still 
a leading cause of disease in the United States. Many wells 
receive drainage from barnyards and cesspools (p. 324), many springs 
used as a source of drinking water are exposed to surface wash and 
to pollution by stock, and many villages and cities use river and 
lake water contaminated by sewage. 

In the interest of public health many cities have discouraged or forbidden 
the use of private wells, and some states have laws designed to prevent the pollu- 
tion of lakes and rivers. Chicago formerly discharged its sewage into Lake Mich- 
igan, from which, at some distance from shore, the city obtains its water. Because 
of danger that sewage would pollute the water supply, the city built the Chicago 
Sanitary and Ship Canal, opened in 1900 at a cost of about $50,000,000, through 
which the sewage is turned into the Illinois River. The sewage of Buffalo goes 
into the Niagara River, the water of which is used for drinking and other purposes 
by several towns, including Niagara Falls. Largely as a result, the typhoid death 
rate is very high at these places. The city of Niagara Falls is "one of the worst 



USES AND PROBLEMS OF INLAND WATERS 463 

plague-spots, if not the very worst, in respect of typhoid fever in the United 
States to-day." Surely, sewage should be disposed of in some better way than by 
putting it into drinking water. It can be used to great advantage, for example, 
on the land, for fertilizing purposes (p. 271). This is now done by some cities, 
especially in Europe. 

For many industrial purposes, the value of water depends on 
the kind and amount of mineral matter it contains. Distilleries 
and breweries require water of exceptional purity. Laundries and 
textile mills need water which is clear, free from iron, and contains 
relatively little other mineral matter. Railroad companies spend 
large sums in treating the waters used in their engines, so as to make 
them less injurious to the boilers. Knowledge of the quality of 
the waters of the country is so important from various standpoints 
that extensive investigations of surface and ground waters are being 
made by the United States Geological Survey, and by various state 
and private agencies. 

Questions 

1. Are cities more likely to develop on the inside or outside of great bends on 
navigable rivers? Give examples and reasons. 

2. Why does the cost per ton for transportation by water tend to decrease 
as the size of the cargo increases? 

3. Why are four-fifths of the population of New York State in the counties 
bordering the Hudson River and Erie Canal? 

4. What things would need to be known in order to determine accurately 
the amount of water power which could be developed in a given area? 

5. (1) Account for the enormous amount of water power available in the 
Northern Pacific district, according to the table on page 443. (2) Why do the 
western tributaries of the Mississippi River afford more power than the eastern 
tributaries? (3) Why does the Northern Atlantic district (p. 443) furnish more 
water power than the Southern Atlantic? 

6. Explain the fact that apples and other fruits are grown in great perfection 
and abundance on irrigated lands around Grand Junction, in western Colorado, 
while in the same latitude in western Nevada attention is given largely to hardier 
crops, such as grain, potatoes, and onions. 

7. Account for the fact that legislation concerning the utilization of stream 
and ground waters is more advanced in western than in eastern United States. 

References 

NAVIGATION 

Brown: A Review of the Waterway Problem, in Bull. Am. Geog. Soc, Vol. 
XLIII, pp. 573-586. 

Bureau. of the Census: Special Report on Transportation by Water, igo6, 
especially pp. 163-195. 



464 ELEMENTS OF GEOGRAPHY 

Burton, T. E., and Others: Preliminary Report of the Inland Waterways 
Commission, especially pp. 18-27, 35-38, 133-136, 150-159, 314-333, 377~435- 
(Gov't Printing Office, 1908.) 

Burton, T. E., and Others: Preliminary Report of National Waterways Com- 
mission (Sen. Doc. 301, 61st Cong., 2d Sess.), especially pp. 3-33; and sundry 
later reports on the rivers and canals of this and other countries. 

Chisholm: Inland Waterways, in Geog. Jour., Vol. XXX, pp. 6-28. 

Dixon: A Traffic History of the Mississippi River System; National Water- 
ways Commission, Document No. 11. (Gov't Printing Office, 1909.) 

Johnson, E. R. (Editor): American Waterways; Annals Amer. Acad, of 
Pol. and Soc. Sci., Vol. XXXI, No. 1. (Contains articles on various American 
canals and rivers.) 

Semple: Influences of Geographic Environment, Ch. XI. (New York, 191 1.) 

Smith, H. K.: Transportation by Water, in Report National Conservation 
Commission (Sen. Doc. 676, 60th Cong., 2d Sess.), Vol. II, pp. 13-56. 

Smith, H. K.: Report of the Commissioner of Corporations on Transportation 
by Water in the United States (1909). (Gov't Printing Office, 1909.) 

water power 

Howe: The White Coal of Switzerland, in Outlook, Vol. XCIV, pp. 151-158. 

Leighton: Water Power in the United States, in Report National Conserva- 
tion Commission, Vol. II, pp. 141-144, 159-163, and Annals Amer. Acad, of Pol. 
and Soc. Sci., Vol. XXXIII, pp. 535-565. 

McGee: Water as a Resource, in Annals Amer. Acad, of Pol. and Soc. Sci., 
Vol. XXXIII, pp. 521-534. 

IRRIGATION 

Blanchard: Home-making by the Government, in Nat. Geog. Mag., Vol. XIX, 
pp. 250-287. 

Blanchard: The Call of the West, in Nat. Geog. Mag., Vol. XX, pp. 403-437. 

Fortier: Irrigation, in Report National Conservation Commission, Vol. II, 
pp. 67-73. 

King: Irrigation and Drainage. (New York, 1902.) 

Newell: Irrigation, in Report National Conservation Commission, Vol. II, 
pp. 59-66. 

Newell: Irrigation in the United States. (New York, 1902.) 

Newell: What May Be Accomplished by Reclamation, in Annals Amer. Acad, 
of Pol. and Soc. Sci., Vol. XXXIII, pp. 658-663. 

DRAINAGE 

Fallonsbee: Swamp and Overflow Lands, in Report National Conservation 
Commission, Vol. Ill, pp. 361-372. 

Herrick: Relation of Malaria to Agriculture and Other Industries of the 
South, in Pop. Sci. Mo., Vol. LXII, pp. 521-525. 

Shaler: Fresh-Water Morasses of the United States, in 10th Ann. Rept., 
U. S. Geol. Surv., pp. 261-312. 

True: Swamp and Overflow Lands, in Report National Conservation Com- 
mission, Vol. Ill, pp. 373-374. 



CHAPTER XVII 




MOUNTAINS AND PLATEAUS AND THEIR RELATIONS TO 

LIFE 

Mountains and plateaus have been referred to frequently in 
earlier pages. The more important points concerning their origin, 
their history, and their relations to human affairs are considered 
in this chapter. 

Mountains 

Distribution of mountains. As already noted, mountain ranges 
are situated in general toward the borders, rather than in the interiors, 
of the continents, and most of the longer and higher systems are not 
far from the edges of the great- 
est ocean basin. The settling 
of the ocean basins, due to the 
shrinking (partly through cool- 
ing) of the earth, may have been 
an important cause of the de- 
formation which has occurred 
near the edges of the continen- 
tal plateaus. This is, however, 
an unsolved problem. 

Leading types of moun- 
tains, (i) Fig. 337 shows 
several mountain ridges of one 

type, and suggests their origin. A plateau or plain was divided by 
giant cracks into a series of great blocks, which were displaced 
(faulted), the relatively elevated edges forming mountain ridges. 
The mountain ridges may be due to uplift, or to the sinking of the 
lower land adjacent to them, or to both. Such mountains are 
called faulted or block mountains. Block mountains in various 
stages of dissection occur in Oregon, Nevada, and elsewhere. 

(2) Mountains consisting of a series of folds formed by com- 
pression from the sides are a common type. In some cases the folds 

465 



Fig- 337- Diagram of block moun- 
tains. (Modified after Davis.) 

What is the age of these mountains, 
in terms of erosion? 

What was the topographic age of the 
surface from which the mountains were 
formed? The evidence? 



466 



ELEMENTS OF GEOGRAPHY 



are open and symmetrical (Fig. 338) ; in others they are closed, unsym- 
metrical, and overturned. In some cases the arrangement of the 
beds is complicated by many faults, some of winch may record a 
vertical displacement of several thousand feet (Fig. 339). The 
present topography of most folded mountains — for example, of 



Fig. 338. Open, symmetrical folds in the Appalachian Mountains. North- 
eastern West Virginia. Length of section, about 12^ miles. The formation 
shown in solid black contains coal. (After U. S. Geol. Surv.) 

the Appalachians and Juras — is not controlled so much by the 
original folding and faulting as by subsequent erosion and warping. 

(3) Many of the higher isolated mountains are volcanic cones 
(p. 302; Fig. 340). Many mountains have been formed also by 
massive intrusions of lava which have domed or lifted the over- 
lying beds high above the level of the surrounding country (Fig. 
177). In many such cases the cover of sedimentary rocks has been 
partly removed by erosion, exposing the central core of igneous 
rocks (Fig. 341). Among the mountains produced chiefly by vul- 




Fig. 339- Folded and faulted strata in the Appalachian Mountains near 
Bristol, Virginia. (After U. S. Geol. Surv.) 



canism and subsequent erosion are the Henry Mountains of Utah, 
and the Park and Elk ranges (Fig. 342) of Colorado. 

(4) There are many mountains which owe their existence simply 
to the resistance of their rocks, which have been left standing in 
bold relief by the removal of the surrounding weaker rocks. Many 
mountain peaks, aside from volcanic peaks, are of this origin. Pike's 
Peak, Colorado, is a notable example. The Catskill Mountains of 
southeastern New York are due to unequal erosion, where the 
resistance of the rock is not very unequal. They are really a dissected 
plateau! Various other maturely dissected plateaus of considerable 
relief are called mountains. 



MOUNTAINS, PLATEAUS, AND LIFE 



467 



(5) Folding and faulting, vulcanism and unequal erosion all 
may be involved in the formation of lofty mountains. Many 




Fig. 340. Mt. Adams from Trout Lake. (Copyright by Kiser Photo Co.) 

mountains, furthermore, have had several periods of growth, 
between which the upraised beds suffered great erosion (Fig. 343). 

The formation of mountains is an extremely slow process, 
probably occupying, for the 
greater ranges, hundreds of 
thousands or even millions of 
years. Many mountains ap- 
pear to be growing now, — for 
example, the St. Elias Range 
of Alaska. 

Destruction of mountains. 
All mountains are destroyed in 
time by erosion, unless renewed 
by vulcanism or uplift. Fur- 
thermore, the erosion of moun- 
tains commences as soon as 
they begin to rise, and con- 
tinues throughout the long 




Fig. 341. An eroded laccolith. Cross- 
section of Mount Hillers, Utah, with ideal 
representation of the underground struc- 
ture. Compare with Fig. 177. (After 
Gilbert, U. S. Geol. Surv.) 



Fig. 342. Cross-section of Elk Moun- 
tains, Colorado. 



468 ELEMENTS OF GEOGRAPHY 

period of their growth, as well as afterwards. As a result, no moun- 
tain due to vulcanism or diastrophism (crustal movements) ever 
had the full height which those processes would have given it, if 
unopposed by erosion. As already pointed out, many mountains 
have been several times nearly or wholly reduced and revived again. 
The length of the life of a mountain which has ceased to grow is 
determined largely by its height, by the resistance of its rocks, and 
by the character of the climate. 

How does the steepness of many mountain slopes influence their erosion? 
Why is rock-splitting generally important on lofty mountains? When the slopes 
are not too steep, mountains may be covered with loose, angular fragments broken 
from the rocks beneath (Fig. 139). Even in arid regions, mountain valleys may 




Fig. 343. Diagram showing structure of the beds in the region of the Santa 
Lucia Range, California. Length of section, about 1 1 miles. (After U. S. Geol. Surv.) 

contain rushing torrents. (Explain.) In general, erosion by mountain streams 
is favored by steep gradients, but rapid cutting sometimes is opposed by the fact 
that the streams are clear (Why?). How does the absence of vegetation on many 
upper mountain slopes affect erosion? What conditions (1) favor and (2) hinder 
wind work on mountain heights? Glaciers are helping in the reduction of many 
lofty mountains (p. 392). In many other mountains with few or no glaciers now, 
the striking results (What are they?) of the work of former glaciers may be seen. 
Mountain scenery is due far more to the agents of land sculpture than to the forces 
of diastrophism. 

The subdued and gentle slopes of the later life of a mountain 
are worn less rapidly than the steeper slopes of its earlier career, 
so that its old age may be longer than its youth and maturity com- 
bined. All lofty mountains are comparatively young, geologically 
speaking; old mountains have been worn low. While very old 
mountains are low, obviously not all low mountains are old. 

Mountains as barriers. Mountains are barriers to the move- 
ment of animals and men, and to the spread of plants (Fig. 344). 
The effectiveness of a mountain barrier depends largely on its height, 
length, and width; on the number, height, and distribution of the 
passes; and on the number of ridges, and the steepness and character 
of their slopes. The high, massive ranges of the Pyrenees, Caucasus, 
and Andes mountains form very effective barriers. The Pyrenees 



MOUNTAINS, PLATEAUS, AND LIFE 



469 



make the best natural inland boundary in Europe, shutting off Spain 
so completely from the rest of the continent that it is said frequently: 
"Africa begins at the Pyrenees." Although high, the Alps Moun- 
tains have several good passes, well distributed; accordingly, they 




Fig. 344. Toltec Gorge, in the mountains of Colorado. Travel even along 
the valley is difficult. (Denver and Rio Grande Railroad Company.) 



form a less serious barrier. The effect of many mountain barriers 
has been lessened by the building of wagon roads and railroads, 
the cutting of tunnels, etc. (pp. 470, 471). In other cases, moun- 
tains are crossed only by a few difficult trails, along which wares 
are taken on pack animals or by human carriers, trained by their 
environment to be climbers and packers. 



47° 



ELEMENTS OF GEOGRAPHY 



Indians carry India rubber, in 150 pound loads, from the upper Purus and 
Madeira rivers up to the Andean plateau (15,000 feet above sea-level), whence it 
is transported on mules to the Pacific coast. Heavy bales of brick tea are carried 
by coolies over the mountains of western China to Tibet. Human beasts of burden 
carry the limited traffic of many other backward mountain regions. 

For a long time, northern and central Europe was excluded by mountains 
from the culture of the leading Mediterranean countries. China is largely shut 
off from the rest of Asia by encircling mountains, a fact of much importance in 
connection with the isolated development and backward state of that country. 
The Appalachian barrier helped to confine the English colonies to the Atlantic 
seaboard for a century and a half. This favored the development of compact 
commonwealths, and permitted much more rapid progress along many lines than 




Fig. 345. Map showing course of Cumberland National Road. 



would have been possible had the colonists spread themselves thinly over a vast 
area, after the manner of the French, who controlled the St. Lawrence gateway 
into the Interior. For years after the Revolutionary War, the Appalachian 
Mountains exerted a decentralizing influence, politically, which threatened the 
integrity of the Union (p. 419). The first great step in their conquest as barriers 
to trade and travel was taken when the Cumberland National Road was completed 
from Cumberland, Maryland, to the Ohio River at Wheeling, in 181 7 (Fig. 345); 
the second when the Erie Canal was opened (1825). Though this canal did not 
cross the Appalachians, it afforded an easy route to the Interior; and the third and 
greatest, when four railroads were finished across them in the 1850's. It is note- 
worthy that these first trans-Appalachian railroads crossed the barrier at the 
north, where it is narrowest, lowest, and has most good passes. Though no longer 
a formidable barrier, these mountains still impose serious engineering and trans- 
portation problems on some of the railroads which cross them. Until the com- 
pletion of the first transcontinental railroad (1869), travel across the western 
mountains and plateaus was so difficult that many people going to California 
chose the 13,000-mile voyage around Cape Horn, or the route by way of the 
Isthmus of Panama. 

The difficulty of crossing high, rugged mountains gives great 
importance to notches or passes in their ridges. Many mountain 
passes are water-gaps or wind-gaps; their formation has been ex- 
plained, and their relation to human affairs illustrated (pp. 358, 360). 



MOUNTAINS, PLATEAUS, AND LIFE 



471 



Trails, wagon roads, and railroads all seek the lowest and most acces- 
sible passes (Fig. 346). They commonly enter the mountains along 
main valleys, and, where necessary, zigzag up the steeper slopes to the 
passes which serve as gateways through the central ridges (Figs. 347 
and 348). In some cases, railroad companies have avoided the last 
part of the ascent by 
tunnelling the moun- 
tain below the pass. 

South Pass (altitude, 
8,230 feet), in central Wy- 
oming, is the most impor- 
tant pass, historically, in 
the Rocky Mountains. 
Through it ran the famous 
Oregon Trail, along which 
many thousands journeyed 
to the grain lands of Ore- 
gon and the gold fields of 
California. Truckee Pass 
(7,017 feet above sea-level) 
affords a relatively easy 
route across the central 
part of the Sierra Nevada 
Mountains. It was used 
first by the California Trail, 
and is used now by the 
Southern Pacific Railroad. 
As the lowest gap in the 
Caucasus Mountains and 
the only one open through- 
out the year, the Dariel 
Pass is of much importance 
to Russia; through it runs 

the great military road to Tiflis. The Pass of Belfort, between the Vosges and Jura 
mountains, connects the Rhone and Rhine valleys, and with them has constituted 
since ancient times one of the most important routes of travel between the Mediter- 
ranean and North seas. The passes in the mountains of northwestern India 
have served repeatedly as gateways through which tribes and armies from central 
Asia have descended to plunder and conquer the people of the plains. 

The difficulties of travel and communication in rugged moun- 
tains shut their inhabitants away from the outer world, helping 
to retard progress. Old customs, fashions, and manners of speech 
are likely to be preserved by mountaineers long after they have 
been abandoned by the people of the more open lowlands. Educa- 
tion is backward and the percentage of illiteracy high; much of the 




Fig. 346. Sketch-map of region about Holli- 
daysburg, Pennsylvania, showing the influence of 
mountain passes upon the course of wagon roads 
and railroads. (From Hollidaysburg Sheet, U. S. 
Geol. Surv.) 



472 



ELEMENTS OF GEOGRAPHY 







Fig. 347. Road zigzagging up mountain slope in Switzerland. Rhone Glacier 
in middle background. 




Fig. 348. Canyon of the Rio de las Animas Perdidas, Colorado. A "double- 
header" train creeping along a narrow ledge. (Denver and Rio Grande Railroad 
Company.) 



MOUNTAINS, PLATEAUS, AND LIFE 



473 



simple clothing, furniture, etc., is home-made; trade in many cases 
is restricted to barter, involving only the absolute essentials of life; 
and social intercourse is restricted seriously, favoring the close 
intermarriage of families and the development of "clans." These 
conditions are illustrated well among the mountaineers of the south- 
ern Appalachians (Fig. 349). They do not exist, of course, in new 
mountain communities established by progressive people from out- 




lUfe ■ 9Sl 



gHHn ^j&mk 



Fig. 349. Homes of mountaineers in the southern Appalachians. 

side, and they have been changed greatly in some long-settled moun- 
tains (e.g., in the Alps) by the coming of summer visitors (p. 482), 
and in other ways. 

Many mountains are important climatic barriers (p. 122), and 
the conditions of life on their opposite sides may be very different. 
The western slopes of the Sierra Nevada Mountains receive an abun- 
dant rainfall; to the eastward stretch broad deserts. Because most 
of its early mines proved disappointing, and the deficient rainfall 
prevented the extensive practice of agriculture, the population of 
Nevada was always small and fell from about 62,000 in 1880 to some 
42,000 in 1900, less than that of the city of Akron, Ohio, at the same 
time. This was the penalty of its position to the leeward of high, 
rain-catching mountains. More recently, the population of Nevada 
has increased because of irrigation and the discovery of new mineral 
wealth. The contrast is even greater between the two sides of the 



474 ELEMENTS OF GEOGRAPHY 

Himalaya Mountains; to the south are the crowded millions of 
India, to the north the scattered, nomadic tribes of Tibet. The 
difference here is not due wholly to the mountains, but largely to 
the great altitude of the plateau on the north side. 

The settlement of mountains. Most lofty mountains are 
accessible with difficulty, and within them the conditions of life are 
hard. In general, therefore, the settlement of rugged mountains 
begins only after the more inviting neighboring lowlands have been 
occupied, and their populations are always relatively sparse. The 
areas of the Adirondack, Catskill, Alleghany, and other mountains 
in eastern United States were blank spaces on the earlier census 
maps (Figs. 437 and 439), and their populations are in most sections 
sparse even now (Fig. 442). A similar situation exists in the western 
mountains, the Rockies in 1900 containing only 0.8 per cent of the 
population of the country. 

Mountain areas are settled first and most thickly in their larger 
valleys. Here the flatter land favors tillage, soils are thicker and 
in most cases more fertile (Why?), the climate is milder, and the 
trails of the upland are replaced by roads. The Shenandoah Valley 
and its southward continuation, the Valley of East Tennessee, were 
among the first areas to be occupied west of the Blue Ridge, soon 
forming a great island of settlement, with fertile farms and prosper- 
ous villages, in the midst of the mountain wilderness (Fig. 437). 
Similarly, the valleys of the upper tributaries of the Missouri River 
attracted the first permanent settlers into the Rocky Mountains 
of Montana. 

The inhabitants of many mountain valleys in Europe and Asia 
are descendants of people who sought refuge there from their more 
powerful enemies. The Basques, who dwell in the western valleys 
of the Pyrenees, are an example. In other cases, the occupation of 
mountain strongholds has permitted people to dominate the 
adjoining lowlands, and levy tribute on their inhabitants. At the 
beginning of the Revolutionary War, four-fifths of the Cherokee 
Indians dwelt within the southern Appalachians, and from their 
mountain villages they repeatedly made sudden attacks on the fron- 
tier outposts of the whites. 

Agriculture in mountains. Outside the valley bottoms, con- 
ditions are unfavorable to agriculture in high mountains, and in 
many places absolutely forbid it. Many slopes are too steep to be 
tilled, consisting either of bare rock or having here and there a thin 



MOUNTAINS, PLATEAUS, AND LIFE 475 

covering of soil which washes easily when cultivated; and with 
increasing height, the climate prevents the raising of crops and 
even the growth of trees and grasses (Fig. 350). Switzerland is 
largely mountainous, and only about 15 per cent of its area is arable 
land. Only */ 7 of the three Alpine provinces of Austria is tillable. 
Less than % of Japan can be cultivated readily. Such conditions 
mean a scanty food supply and a constant tendency toward over- 
population. As a result, 
there has been persistent 
emigration from many 
mountainous countries, 
such as Norway. These 
conditions mean also that 
in many long-settled moun- 
tain regions the cultivable 
land is farmed intensively 
in small holdings. Every 
effort is made to maintain 
the fertility of the soil, so 
that it may return large 
yields continuously. To 
this end, for example, the 
stock is herded closely at night in some regions, so that the manure 
may be saved for the land. Even from pasture lands where the stock 
roams by day, the manure is carefully gathered, in some of the moun- 
tains of Europe and Asia, and applied to the soil. 

In many mountain regions, where the level land has been 
developed fully, the slopes, too steep for agriculture by ordinary meth- 
ods, have been utilized by the construction of terraces. Retaining 
walls are built one above another on the slopes, and the spaces behind 
filled in and covered with soil, which, in many cases, is brought by 
hand from considerable distances. In this way, successive tiers of 
nearly level benches are made. Terrace agriculture is practiced 
in parts of Arabia, India, China, Italy, Germany (Fig. 351), France, 
Switzerland, and other countries. (Why, in many cases, are the 
terraces built by preference on south-facing mountain slopes?) In 
the European countries mentioned, much terraced land is used 
for vineyards. Choice fields with bearing vines equal in price the 
best irrigated fruit lands of western United States (p. 448). 

The crops which may be grown in mountains vary with the expo- 



- "' . 5. 


.*Mt 




^^tfi 






,^. 


~c3&. "■■• — „ 


—■ ..- 


' 



Fig. 350. Dwarf white pine at timber line 
in Sierra Nevada Mountains. (Fairbanks.) 



476 ELEMENTS OF GEOGRAPHY 

sure, the altitude, the rainfall, the character of the soil, etc. In 
general, the slopes of a lofty mountain present successive climatic 
zones to which plant life, and animal and human life as well, are 
adjusted. If such a mountain is situated in low latitudes, its 
slopes may afford conditions ranging from those of the Tropics 
to those of the Polar Zones (p. 38). In the Alps, the following 
changes may be noted: (1) In suitable places on the sides of the 
lower valleys there are vineyards, olive orchards, and mulberry 




Fig. 351. Terraces along the Rhine Valley. (Butts.) 

groves worked intensively by a relatively dense population. (2) 
Higher up, these are replaced by grain fields and pasture lands, 
interspersed with forests of deciduous trees. This zone is less pro- 
ductive and settled less thickly than the first. (3) Still higher, 
hardy evergreen trees prevail, the proportion of useless land increases, 
only the hardiest grains are grown (up to about 5,300 feet) in small 
fields by the sparse population, and most of the land with soil is 
devoted to pasturage and to the growing of hay for the winter feed- 
ing of the stock. (4) Above Xhz u tree-line' 1 ' (the upper limit of tree 
growth is about 7,600 feet) is a belt in which some of the slopes bear 
grass, where cows, sheep, and goats are pastured for a short time in 
summer. (5) Finally, there is a waste of bare, rocky slopes and 
snow-fields, unoccupied by life which is useful to man. 

Stock-raising in mountains. Stock-raising is an important 
mountain industry in many countries, for slopes too steep or too 
rocky to be tilled, or too high to permit cultivated crops to ripen, 



MOUNTAINS, PLATEAUS, AND LIFE 477 

may afford pasturage (Fig. 352). As suggested above, pasturing 
stock and growing feed for its consumption during the winter con- 
stitute a leading industry in the higher Alps. More than half the 
productive area of Switzerland consists of pasture land and hay 
land. In spring, herdsmen take their cattle, goats, and sheep from 
the villages in the valleys up to the high pastures, advancing, as 
the growth of the grass permits, close to the snow-line (Fig. 353), 















H^W 






^^^^___^ 




HPP^5»* l *^**7'^i 








^ -\\\/ 






V 






•;*; ! ?,*{\v.* 




'- 1 -^W ; 


' 


to*. 








- 


. 






, ' 












V, 


• 




.. ' ! : 






-',■... "Nv- 


.; 


S£j~ 


.. 




$." 


V V. - „ 







Fig. 352. Sheep grazing on a mountain side in Holy Cross National Forest, 
Colorado. (U. S. Forest Service.) 

where 'the grazing season may last only six or seven weeks. In 
autumn, the flocks and herds are driven back by stages to the lower 
valleys, where they are fed in stables during the long winter. As in 
various other countries, most of the high pastures of Switzerland are 
not owned privately, and their use is regulated by custom or law. 
The raising of sufficient hay and other fodder for the winter feeding is 
perhaps the most difficult part of the industry, and this requires 
arduous labor during the summer. For many years butter and cheese 
have been leading products of Switzerland, and emigrants have 
taken the industry to various other countries. For example, making 
"Swiss cheese" is an important industry in certain counties of Wis- 
consin. Stock-raising of one kind or another is a leading occu- 



478 



ELEMENTS OF GEOGRAPHY 



pation in the mountains of Norway, Germany, central Asia, west- 
ern South America, western United States, and elsewhere. 

In western United States great numbers of cattle and sheep feed on the grass 
of the public domain. The use of the unreserved and unappropriated portions 
of the public domain is free and unrestricted. While this has had its advantages, 
it has resulted, at many times and places, in the overstocking of the range, and a 
decrease in its capacity. Some system of regulation is likely to be adopted soon. 
Grazing in the National Forests is regulated now. The Government limits the 




Fig- 353- Summer grazing in the High Alps. 

total amount of stock for each forest, and the superintendent of the forest divides 
the range among the applicants, giving the nearby settlers, with little stock, first 
consideration; then, in turn, the local residents with larger herds, who have used 
the range regularly, the regular users from a distance, and the owners of tran- 
sient stock. A small fee is charged for the use of the range. During a recent 
year more than 25,000 grazing leases were issued, under which great numbers 
of sheep (Fig. 354), cattle, and horses were pastured. 

Mining in mountains. Many mountains contain valuable ore 
deposits, and mining is one of the most distinctive of mountain indus- 
tries. On the other hand, many mountains are not known to con- 
tain ores or mineral matter of commercial value, while various ores, 
and numerous mineral substances which are not ores, are mined 
in plateaus and plains. The original source of most of the valu- 
able metals appears to have been the igneous rocks, and massive 
intrusions of the latter form the central cores of many mountains. 



MOUNTAINS, PLATEAUS, AND LIFE 



479 



The metals probably were scattered widely through the igneous 
rocks to begin with, and were slowly concentrated into ores in veins, 
largely by ground-waters (p/331). These veins are, for the most 
part, in or near the igneous rocks. Many of them have been exposed, 
and so made available to man, by erosion. The iron and copper 
of the Lake Superior region occur in the rocks of old, worn-down 
mountains. Much of the gold mined in the West has come from 




Fig. 354. Sheep grazing in the San Juan National Forest, Colorado. 
Forest Service.) 



(U. S. 



igneous rock, and from the immediate surroundings of great intru- 
sions of lava. In northeastern Pennsylvania the folding of beds of 
rock containing layers of coal helped to change the latter into "hard" 
or anthracite coal. Much of the coal of this region was destroyed 
later by erosion, but much was preserved in the down-folds of the 
mountains (Figs. 355 and 338). More than 80,000,000 tons of this 
coal are mined yearly at Scranton, Wilkesbarre, and other points, 
and much of it is sent throughout eastern and central United States. 
Cities have grown quickly from rude mining camps following the 
discovery of rich mineral deposits (Fig. 356). Thus in the late 
1870's Leadville, Colorado, became a city of 15,000 people in a 
few months, though in a sage-brush valley then difficult to reach, 
and at an elevation of 10,000 feet. In 1880, it shipped more than 



480 



ELEMENTS OF GEOGRAPHY 



a million dollars worth of gold, silver, and lead each month. Again, 
important mineral deposits may help to concentrate a dense urban 
and industrial population about the borders of the mountains in 





Fig- 355- Coal stripping near Hazleton, Pennsylvania. The coal (shown 
at the left) occurs in down-folded (synclinal) beds. Steam shovel for loading coal 
at right. (Roorbach.) 

which they occur, as in the case of the Pennine Mountains of north- 
central England, and the Erz (meaning ore) and Riesen ranges of 
Germany, where mining has been carried on for many years. 




Fig. 356. Bisbee, Arizona, a city which grew up about copper mines. 



Mountains as forest reserves. The slopes of many moun- 
tains have been left largely in timber, because unsuited to agricul- 
ture, and various mountain ranges now support important lumber 



MOUNTAINS, PLATEAUS, AND LIFE 481 

industries (Fig. 357). The relation of mountain forests to the flow of 
streams rising in them, and to the problems of navigation, water power, 
irrigation, and soil erosion has been noted (pp. 269, 444, 455). These 
problems, together with the need of insuring a permanent lumber sup- 
ply, have led various countries to regulate the use and cutting of moun- 
tain forests, and to provide that certain areas remain forest-covered. 




Fig. 357. Modern lumber mill in the Sierra Nevada Mountains, California. 
(U. S. Forest Service.) 



Japan has many steep volcanic mountains, whose slopes, if uncovered, would 
be eroded rapidly by the abundant (Why?) rains; this helps to explain the fact 
that nearly 3/ 5 of the country has been left in forest reserves, although the nation 
is in great need of more farm land. Among European countries, Germany, Switzer- 
land (Fig. 358), and France have skillfully-managed forest reserves on mountain 
slopes. France is said to have more torrential streams than all the rest of Europe, 
and forest destruction on mountain slopes in earlier years increased greatly the 
number and violence of floods. In recent years the government has spent large 
sums in reforestation. Switzerland gave attention very early to the preservation 
and care of mountain forests; in some places forest regulations were in force 600 
years ago. Some of the Mediterranean countries show the evils which may follow 
the cutting away of mountain forests. In Dalmatia, for example, mountain 
slopes once forested consist now of bare rock, and are of little use to man. 
In parts of eastern and northeastern China the forests are gone, and one may 
travel hundreds of miles without seeing a single grove on the hill sides. Even 
the undergrowth has been destroyed, and in places all grass and other vege- 



482 



ELEMENTS OF GEOGRAPHY 



tation suited to the purpose are gathered for the cattle, or eaten by goats 
and sheep. 

Serious results have followed: (1) Heavy rains cause sudden and violent 
floods. Valleys usually without streams may be occupied suddenly by torrents 
which destroy bridges and buildings, ruin fields, and then disappear entirely 

within a few hours. (2) 
In many places not enough 
water enters the ground to 
keep the water table suffi- 
ciently near the surface for 
the good of plants. Far- 
mers irrigate where they 
can, and grow plants suited 
to dry conditions, but over 
large areas they are unable 
to grow anything. (3) 
Erosion has been increased 
enormously (Fig. 143). 
Large lowland areas are 
covered with coarse waste, 
and much fine material is 
swept into the sea. (4) 
Timber is at a premium. 
In the western mountains 
forest destruction is less 
advanced, and travellers 
report meeting long lines 
of coolies carrying boards 
down to the plains, where 
they are worth the equiva- 
lent of $2 to $3 each, a 
value which restricts their 
use to special purposes, 
such as making coffins. 

Most of the National 
Forests of the United 
States (p. 455) are in the 
mountainous districts of 
the West (Fig. 336), where 
the greater part of the 
timber is found on the 
mountain slopes because the latter receive more rain than the surrounding plateaus 
and plains. Congress provided recently (Feb., 191 1) for a National Forest in the 
southern Appalachians, where the maintenance of a forest cover on many of the 
slopes is of great importance (pp. 275, 342). 

Mountains as pleasure resorts. The cool, invigorating sum- 
mer climate and beautiful scenery of many mountains lead thousands 




Fig. 358. Mountain slopes in Switzerland, kept 
under a forest cover. (Doseff.) 



MOUNTAINS, PLATEAUS, AND LIFE 



483 



of lowland dwellers to visit them yearly. The mountains of New 
England, the Adirondacks, Catskills, and parts of the Alleghanies, 
are readily accessible to the more densely settled northeastern part 
of the United States, and contain many popular resorts. With 
the growth of population in western United States, the mountains 
of that section probably will be visited more and more. 

Most of the National Parks (Fig. 359) and National Monuments are in the 

! West, and a number of them contain mountains or portions of mountains of unusual 

beauty and interest. The National Parks, of which there are 13 in continental 




Fig 359- Map showing distribution of National Parks. (U. S. Dept. Int.) 



United States, were created by Congress, and serve various purposes; they are 
intended especially to be "play-grounds for the American people." In 1905 the 
President was given power to set aside from the public domain as National Monu- 
ments any "historic landmarks, historic or prehistoric structures, or other objects 
of historic or scientific interest." There are now more than twenty National 
Monuments, of which the Mount Olympus, Washington, and Grand Canyon, 
Arizona, monuments are largest. 

The Alps, situated in the midst of densely settled countries, 
are the most beautiful mountains in Europe, and have come to 
be perhaps the greatest summer resort in the world. Hundreds 



4 8 4 



ELEMENTS OF GEOGRAPHY 



of hotels (Fig. 360) depend upon the tourist trade, and the enter- 
tainment of visitors has become almost a national industry. 

Other mountain resources and industries. Fur-bearing animals 
constitute an important resource of some mountain regions. They 
were once a resource in many others where they have been nearly 
exterminated. 

From about 1807 to the middle of the century, the fur trade in the Rocky 
Mountains of the United States was of great value. Trading posts were estab- 
lished at commanding points among the mountains and along the larger rivers 




Fig. 360. A summer hotel in the High Alps. 



flowing eastward from them, at which a driving business was done. St. Louis 
was the great depot and outfitting point of the trade. The trappers and traders 
were the pathfinders of the West. The fur trade is still of some importance in 
the mountains of western Canada. 

We have noticed already that many isolated mountaineers 
are forced to make most of their own clothing, implements, uten- 
sils, etc. (p. 471). In addition, many mountain peoples make special 
articles of superior quality for sale. In this way they eke out a 
living, and find employment during the winter months when most 
outdoor activities are suspended. From wood, metals, wool, or 
other raw material at hand, they make artistic wares which are 
suited to mountain transportation, and command ready sale. Such 
are the carved wooden wares of the Swiss, and the lace made by 
some of the Italian mountaineers. 



MOUNTAINS, PLATEAUS, AND LIFE 485 

Many mountain streams afford abundant water power (pp. 383, 
393, 444) which will be used increasingly in the future. In most 
cases, however, much of the energy will be carried outside the moun- 
tains in the form of electricity, to be used in the lowlands. 



Plateaus 

Distribution. As stated elsewhere (p. 37), large plateaus occur 
for the most part in three classes of situations. (1) Some of them are 
between a lower plain on one side and higher mountains on the 
other, (2) some are between mountain ranges, and (3) some rise 
abruptly from the sea, or from narrow coastal plains. 

Origin. Plateaus are formed in various ways. (1) Some have 
been built by successive lava flows, like the Columbian Plateau of the 
Northwest (Fig. 176) and the Deccan Plateau of India. (2) Adjacent 
land may have been worn low or warped down, leaving a plateau. (3) 
The plateau may have been warped or faulted above its surroundings. 

The erosion of plateaus. Like mountains, all plateaus will be 
worn down to lowlands, if not made high again. Mature plateaus 
are table-lands well dissected by streams; the surface is carved into 
hills (or mountains) and valleys (or canyons), and slope and relief 
are at a maximum. Some dissected plateaus are called mountains 
(e. g. the Catskills, p. 466). In one sense there are no old plateaus, 
for, when worn low, they are plains. 

Conditions of life on plateaus. The conditions of life on 
high, dissected plateaus are much like those in mountains situated 
similarly (pp. 471—481), while the conditions on many low plateaus 
resemble closely those on neighboring plains (Chapter XVIII). 
Large, mountain-rimmed plateaus in continental interiors are, in 
general, deserts, and subject to great ranges in temperature. Accord- 
ingly, they are settled sparsely. Farming is confined for the most 
part to the slopes of waste at the bases of rain-catching mountains, 
where water may be led from the withering streams for use in irri- 
gation. The greater part of such plateaus is uninhabited, save 
by bands of wandering nomads, as in Central Asia, or by occasional 
ranchmen whose cattle and sheep graze on the thin and scattered 
growth of grass, as in parts of western United States. 

The habitability of a high plateau is influenced greatly by its 
latitude; while such a plateau is cold and uninviting in the Temperate 
Zone, it has a temperate climate in the Tropics, where, if other 



486 



, ELEMENTS OF GEOGRAPHY 



conditions are favorable to occupation, it may have a population 
much denser than that of the neighboring lowlands. 

Nearly three-fourths of the people of Bolivia live at altitudes of 6,000 to 
14,000 feet, and of the nine most thickly settled provinces, five are at elevations 
greater than 11,000 feet. Three-fourths of the population of Ecuador are found 
in the plateau basins of the Andean highlands, at an average elevation of 8,000 
feet. In Peru there is a comparatively dense plateau population. There is a 
striking contrast also between parts of the cool plateau and the hot lowlands of 
Mexico. The former have relatively dense and progressive populations, while 
the latter are settled sparsely by backward Indians. In higher latitudes, plateaus 
for various reasons are in general settled much less densely than the neighboring 
plains, as already indicated. The Great Basin and Columbian Plateau of western 
United States each contained, in 1900, only 0.5 per cent of the population of the 
country. In these regions the population 'numbered only 1.6 and 3.2 persons, 
respectively, per square mile. The sparsest population of Great Britain is found 
in the Highlands of Scotland, the county of Sutherland having only n inhab- 
itants per square mile. 



Questions 



1. (1) In what stage of erosion are the mountains shown in Fig. 361? (2) 
Does the picture indicate (certainly, probably, possibly) anything concerning 
the character of the rocks? (3) How will the slopes of these mountains be changed 

in the future? 




Fig. 361. Sketch of mountainous region. 



2. (1) Compare and contrast the 
climate of the mountains and plain 
shown in Fig. 362. Why the dif- 
ferences? (2) What work are the 
streams doing in the mountains? On 
the plain? Reasons in each case? 
(3) What kinds of soil would you 
expect to find on the plain just west 
of the mountains? Why? (4) What 
does the map suggest concerning the 
chances for successful agriculture in 
the different parts of the area? 

3. (1) Why is there a cliff on the slope shown in Fig. 363? (2) What was the 
origin of the rocks of which the cliff is composed? (3) How and by what agents 
will the character of the cliff be changed in the future? (4) Account for the dif- 
ference in the amount of vegetation on the upland and lowland. (5) Will soil 
form quickly or slowly on the talus slopes? Why? 

4. Compare and .contrast the relations of mountains to the life of (1) primitive 
and (2) advanced peoples. 

5. What probably would have been the effect upon the development of the 
United States had the Appalachian Mountains been equal in height to the Rockies 
or Sierra Nevadas of to-day? What if the western mountains had been as low 
as the Appalachians? 

6. Account for the fact that houses in arid plateaus often are built with fiat 
roofs and thick walls. 



MOUNTAINS, PLATEAUS, AND LIFE 



487 



References 

Barrett: Features of Norway and Its People, in Jour, of Sch. Geog., Vol. V, 
pp. 241-249, 294-302. 

Bowman: The Distribution of Population in Bolivia, in Bull. Geog. Soc. of 
Phil., Vol. VII, pp. 74-93. 




Fig. 362. Portion of Paradise, Nevada, topographic sheet. Scale 4 miles 
per inch. (U. S. Geol. Surv.) 



Brigham: Geographic Influences in American History, Chs. I, III, IX. 

Dana: On the Origin of Mountains, in Am. Jour. Sci., 3d Series, Vol. V, 
PP- 347-350, 423-443; Vol. VI, pp. 6-14, 104-115, 161-172. 

Davis: The Mountain Ranges of the Great Basin, in Bull. Harvard Mus. of 
Comp. Zool., Vol. XLII, pp. 129-177. 



488 ELEMENTS OF GEOGRAPHY 

Davis: An Excursion to the Plateau Province of Utah and Arizona, in Bull. 
Harvard Mus. of Comp. Zool., Vol. XLII, pp. 1-50. 

Dodge: Life on the Colorado Plateaus, in Jour, of Sch. Geog., Vol. IV, pp. 45-51. 

Dutton: The Geology of the High Plateaus of Utah, U. S. Geog. and Geol. 
Surv., Rocky Mtn. Region. (Washington, 1880.) 

Geikie, J.: Mountains, in Scot. Geog. Mag., Vol. XVII, pp. 449-459. 

Gilbert: Origin of the Physical Features of the United States, in Nat. Geog. 
Mag., Vol. IX, pp. 308-317. 

Herbertson: Man and His Work, Ch. VI. (London, 1908.) 

Howarth: The Cordillera of Mexico and Its Inhabitants, in Scot. Geog. Mag., 
Vol. XVI, pp. 342-352. 




Fig. 363. Cliff in eastern part of Bighorn Basin, Wyoming. (Darton, U. S. 
Geol. Surv.) 



Le Conte: Theories of the Origin of Mountain Ranges, in Jour, of Geol., 
Vol. I, pp. 543-573- 

Powell: Physiographic Features, in Physiography of the United States, 
pp. 33-64. (New York, 1895.) 

Powell: Physiographic Regions of the United States, Idem, pp. 65-100. 

Reade: The Origin of Mountain Ranges. (London, 1886.) 

Semple: American History and Its Geographic Conditions, Chs. Ill, IV, X, 
XL (New York, 1903.) 

Semple: The Anglo-Saxons of the Kentucky Mountains, in Bull. Amer. Geog. 
Soc, Vol. XLII, pp. 561-594. 

Semple: Influences of Geographic Environment, Chs. XV, XVI. (New 
York, 1911.) 

Smith, J. R.: Plateaus in Tropical > America, in Report of Eighth Interna- 
tional Geographical Congress, pp. 829-835. (Washington, 1905.) 

Willis: The Mechanics of Appalachian Structure, in 13th Ann. Rept., U. S. 
Geol. Surv., Pt. II, pp. 211-283. 
Folios of U. S. Geol. Surv. of areas in mountainous districts. 

See also list of textbooks on page 312. 



CHAPTER XVIII 
PLAINS AND THEIR RELATIONS TO LIFE 

Origin and classes of plains. Various types of plains have 
been discussed in previous pages, and some of their relations to 
human affairs noted. Rivers make flood-plains (p. 364), delta plains 
(p. 372), and peneplains (p. 351). The ancient ice-sheets covered 
large areas of northern United States and Europe with drift, form- 
ing drift plains or glacial plains (p. 398). The floors of extinct 
lakes form many nearly flat lake plains, especially in glaciated regions 
(p. 400). Most lake plains are small. 

Extensive plains, like the Atlantic and Gulf coastal plains of 
the United States and the vast interior plain which stretches from 
the Appalachians to the Rockies, cannot in most cases be put in 
any of the above classes. They commonly contain many smaller 
plains of several or all of the types mentioned. In general, exten- 
sive coastal plains are former marginal sea-bottoms, exposed either 
by elevation of the land or by lowering of the sea. Coastal plains 
may also be peneplains, or the result of the filling of a shallow sea 
border by wash from the land. Large interior plains are either 
areas once high but now worn low, or, in a greater number of cases, 
they are former coastal plains now separated from the sea by newer 
land. The changes produced on plains by erosion were discussed 
in Chapter XV. 

Distribution of extensive plains. Most of the extensive plains of 
the world are in the northern hemisphere. The northern parts of the 
large plains which border the Arctic Ocean are of little value to man, 
but there are vast, fertile plains in the north temperate zone which 
are of great importance in the life of the world. The southern conti- 
nents are unfortunate in having their most extensive lowlands within 
the tropics, where climatic conditions retard human progress. 

General advantages of plains. From the standpoint of human 
occupation, plains which possess a favorable climate have distinct 
advantages over mountains and plateaus. In general, the slopes 

489 



I 



490 ELEMENTS OF GEOGRAPHY 

of plains are gentler, their soils thicker and more fertile, and they 
have a much smaller percentage of useless land. Their advantages 
of climate, soil, and topography make plains the great agricultural 
regions of the world. In this connection it should be remembered 
that agriculture is the basis of all permanent advance in civilization 
Movement is relatively easy on plains, and difficult in mountains 
(p. 468). This means that commodities and ideas circulate more 
readily, and that trade and culture develop more rapidly, among 
lowland people. There is a constant exchange, conflict, compari- 
son, and accumulation of the ideas of many — a continual com- 
petition which spurs to progress. In mountains, a great variety of 
conditions may be found within a small area, while on plains, similar 
conditions may prevail over large areas. It follows that most occu- 
pations of plains have a much wider distribution than those of moun- 
tains. The effect of thin air on the human body (p. 45) helps to 
restrict man to relatively low lands. 

Because of ,the fundamental advantages of lowlands for agri- 
culture, trade, and intercourse, the great majority of the people of 
the world live on them. The relatively dense populations of the 
favored lowlands of the United States are shown by Fig. 442. The 
accompanying table shows the percentage of the total population of 
the United States at various altitudes in 1880 and 1900. In both 
years, more than 9 /io of the people lived at elevations of less than 
1,500 feet. While this reflects the fact that most of the people of 
the United States live on plains, it will be remembered that there 
are plateaus and mountains lower than 1,500 feet, while a part of 

the Great Plains is much higher. 

Per cent, Per cent, 

Altitude 1880 1900 

Below 100 feet 15. 1 159 

100- 500 feet 23 . 1 21.8 

500- 1000 feet 40.5 38. 7 

1000- 1500 feet 14.6 14. 7 

1500- 2000 feet 3.5 4.1 

2000- 3000 feet 1.6 2.1 

3000- 4000 feet 0.2 0.5 

4000- 5000 feet 0.3 0.7 

5000- 6000 feet 0.3 0.6 

6000- 7000 feet 6.3 0.4 

7000- 8000 feet 0.2 0.2 

8000- 9000 feet 0.1 0.1 

9000-10000 feet 0.1 0.1 

10000-and above 0.1 0.1 



LIFE IN PLAINS 491 

Contrasts among plains. Apart from their mode of origin, plains 
differ in many respects. Thus they may be large or small, high 
or low, rough or smooth, forested or treeless, fertile or infertile, wet 
or dry, and in hot, temperate, or cold regions. Furthermore, 
all gradations occur between the extremes indicated. These dif- 
ferences affect human interests in important ways, many of which 
have been noted. 

Relatively small plains protected by natural barriers, rather than large, open 
ones, favor early progress in civilization. A restricted area hastens advance to the 
agricultural stage (Why?), and as the population increases in density, laws and 
customs are developed in the attempt to overcome the friction which goes with 
crowding. The isolated and protected plains of Greece possessed many advan- 
tages for early progress. On the other hand, all parts of a vast plain, such as that 
of Russia, are open to attack; it is easy for the people to scatter in search of game 
and other food; and the natural food supply may be sufficient to postpone indef- 
initely further progress. Extensive plains, such as those of central United States, 
afford excellent conditions for the further growth and development of a people 
already advanced in civilization. This is especially true where, as in the case cited, 
such plains have varied geographic conditions and resources in their different 
parts. The vast plains of Russia lack such diversity to a marked degree, and this 
is held by many to have been an important factor in producing the monotony 
characteristic of Russian country life. 

Climate is the most important factor affecting the life of exten- 
sive plains, and the larger plains of the world are so distributed 
with reference to climate that the conditions of life in them may 
be discussed briefly under the following headings: (1) Life in well- 
watered plains of middle latitudes. (2) Life in semi-arid plains. 
(3) Life in desert plains. (4) Life in Arctic plains. (5) Life in 
humid plains of low latitudes. The more important direct effects 
of various types of climate on life were discussed in Chapters IX, 
X, and XL 

Life in Well- Watered Plains of Middle Latitudes 

The middle-latitude plains having adequate rainfall are the 
seats of advanced civilizations, and some of them support dense 
populations. The soil is the most important natural resource of 
these plains, and agriculture is the most wide-spread occupation. 
On the whole, they have less than certain highlands in the way of 
forests, minerals, and water power, though they are by no means 
without these resources. Lumbering and mining are carried on 
at many points, and commerce and manufacturing are developed 



4Q2 ELEMENTS OF GEOGRAPHY 

highly in the more densely settled sections. In the complex life 
of these regions, the influence of geographic conditions is less appar- 
ent and less direct, but not less important, than in the simpler life 
of the grasslands and deserts. 

Differences in the character of the soil, in the form of the land, in conditions 
of drainage, etc., may be reflected in the distribution and occupations of the people. 
The influence of variations in soil is especially great, and may be observed in many 
places. In the glaciated plains of northern United States, various kinds of soil 
may occur within a small area, in places even within the limits of a good-sized farm. 
Here the intelligent farmer is likely to devote each type of soil to the particular 
use or uses to which it is adapted. In other places, the character of the drift over 
several or many square miles is determined by the nature of the underlying rock, 
so that, for example, an area of sandy drift, over sandstone, may lie beside an area 
of limey clay, over limestone. In such a case in a certain region in south central 
Wisconsin, the condition of the people in the two areas is very different. The 
area of fertile, limey-clay soil is said to have been settled by people of greater 
means, while the sandy area was occupied by poorer people not in a position to 
choose. The initial difference appears to have increased. In the one case, there 
are attractive homes that have modern conveniences, there are large barns, many 
windmills, improved roads, and many well-equipped schools; in the other, many 
of the buildings are old and unpainted, few farms have windmills, roads are poor, 
and some of the schools are in an unsatisfactory condition. 

The influence of soil on the distribution and activities of people may be seen 
on a larger scale in various parts of the Atlantic and Gulf coastal plains. In 
Alabama, the northern part of the state is underlain by old rocks (Fig. 364). 
This section was land when the area of the coastal plain was a marginal sea-bottom. 
Material washed from the old land helped to build the strata of the coastal plain. 
East and west across the middle of the state is a low, nearly level belt of rich soil, 
weathered from the soft underlying limestone. This is the inner part of the coastal 
plain. From its southern edge the ground rises rather abruptly some 200 feet, 
because of the outcrop of more resistant beds, and then slopes gently southward 
to the coast. The soils of this outer belt are much poorer than those of the inner 
lowland, except along the bottoms of the larger valleys, where there are deep, 
fertile loams. The development and present life of the state cannot be understood 
apart from these soil belts. The first American settlers, typical log-cabin pioneers, 
settled for the most part in the rich inner lowland and along the fertile valley 
bottoms. Later, this was seen to be the section best suited to the growth of cotton, 
and many of the earlier settlers were pushed by the slave-owning planters north 
into the foothills of the mountains, or south into the sandy areas of the outer 
coastal plain. The inner lowland contained the largest number of slaves at the 
time of the Civil War (Fig. 365), and more than 3/5 of its present population are 
negroes. Here also are the cities of Montgomery and Selma. The outer zone of 
the coastal plain always has had a relatively sparse population, except along the 
larger valleys. There are still extensive pine forests where lumbering, the making 
of turpentine, and grazing are leading industries. Mobile is the only important 
city in this section of the state. It has a harbor at the drowned mouths of the lead- 
ing rivers of the region, and is the natural gateway into the state from the south. 



LIFE IN PLAINS 



493 



In the Netherlands, the Frisian, Saxon, and Frankish elements of the popula- 
tion for the most part occupy contrasted soil areas in the western and northwestern 
eastern, and southern parts of the country, respectively. "All the types have 
maintained their differences of dialect, styles of houses, racial character, dress and 
custom." The soil belts of the ancient coastal plain of eastern England are said 
to have influenced in important ways the development and life of the region. 




Fig- 364- Fig- 365. 

Fig. 364. Map showing principal physiographic provinces of Alabama. 
Fig. 365. Map showing distribution of slaves by counties in Alabama (i860). 
Figures in legend indicate percentages of the total population. 



Life in Semi-Arid Plains 

Large semi-arid plains occur in the belt of the trade-winds, where 
some of them merge into deserts, as in northern Africa and Australia. 
Others lie in continental interiors to which the dominant winds 
come robbed of most of their moisture in passing over mountains, 
as in the case of the steppes of western Asia and the Great Plains 
of the United States. The scanty rainfall of such plains or its 
unfavorable distribution prevents the growth of most trees except 



494 



ELEMENTS OF GEOGRAPHY 



along the streams, and restricts useful vegetation to quick-growing 
grasses and a few other hardy types of plants. 

Hunting tribes and pastoral nomads. Under primitive con- 
ditions, the inhabitants of the grass lands of the world derive their 
support from flocks and herds, or depend on the chase, like the 
buffalo-hunting tribes of earlier years on the Great Plains (p. 496). 
Both the pursuit of game, and the frequent need for fresh pastures 
with new supplies of water, condemn the people to a nomadic life, 




Fig. 366. 
Adams.) 



Home of native nomad of Argentine Patagonia. (Harriet Chalmers 



and so help to retard progress in civilization. The dwellings must 
be such that they can be moved easily (Fig. 366), and in many cases 
they are tents of skins, or of felt made from wool; personal effects 
and household utensils are few and light; and among pastoral nomads 
the most desirable form of wealth is flocks or herds, which transport 
themselves. 

The movements of many pastoral tribes are regulated by the 
seasons. In some cases, their flocks and herds are driven in summer 
into the highlands, thus escaping from the hotter plains and utilizing 
more of the pasturage. The Kirghiz of Russian Turkestan regularly 
take their flocks in summer up into the Altai Mountains, and bring 
them back to the lower lands in winter. Again, the more abundant 
grass and water of the rainy season may permit the people to gather 



LIFE IN PLAINS 495 

in considerable groups in desirable localities, while in the dry season 
they are forced to scatter widely, to secure food for their animals. 

Less strikingly than the men of the desert (p. 502), the pastoral 
nomads of semi-arid plains have always been marauders and con- 
querors. Under favorable conditions, their growing herds and 
flocks require more and more pasture, and from time to time compel 
them to move beyond the boundaries within which they formerly 
had roamed. On the other hand, severe and protracted drought, 
resulting in reduced pasturage and a failing water supply, or disease 
among their animals, may reduce them to the verge of famine, and 
drive them to pillage and conquest. The active, hard life of the 
pastoral nomad serves as an excellent training for military service. 
Constant exposure and exertion develop endurance and bravery, 
while the frequent moving of tents and flocks from one place to 
another results in many cases in an effective organization, well 
suited to military needs. Mounted on horses or camels, the nomads 
are able to make swift attacks on the people of neighboring districts, 
and to retreat as quickly with their booty. History furnishes many 
examples of the lasting antagonism between the militant nomads 
of dry plains and the peacefully inclined farmers of moister lands. 
For centuries, portions of agricultural Russia were pillaged repeatedly 
by hordes of horsemen from the southeastern steppes, and the Great 
Wall of China was built as a protection against pastoral nomads. 

In general, it may be said that the conditions of life in semi- 
arid, grassy plains rarely, if ever, permit the native tribes occupying 
them to develop more than a low form of civilization. 

Use of semi-arid plains by civilized people. Even where 
civilization is advanced, plains that are too dry for agriculture by 
ordinary methods are devoted largely to the grazing industry. Vast 
semi-arid areas used in this way occur in the United States, Argen- 
tina, Australia, and Russia. More than X A of the world's cattle 
and nearly x /i of the world's sheep are owned in the United States. 
By no means all these animals are found either in plains or in regions 
of deficient rainfall, but under modern conditions such districts 
constitute the typical grazing areas. 

By means of irrigation and special methods of cultivation, agri- 
culture doubtless will be extended greatly in the future in semi- 
arid regions. 

The Great Plains. The history of the western portion of the 
Great Plains illustrates many of the conditions of life in semi-arid 



496 ELEMENTS OF GEOGRAPHY 






regions. Until after the Civil War, these plains were occupied by 
Indians dependent for a living on the great herds of buffaloes. The 
practical extinction of the buffalo and the rounding up of the Indians 
on the reservations opened the region to the cattle industry. In 
the drier sections, attempts to farm by ordinary methods have 
been generally unsuccessful, though here and there streams and wells 
furnish water for irrigation (p. 498). Within the last few years, 
"dry farming" (p. 498) has replaced the grazing industry in many 
places. 

As already indicated, the buffalo was the most important factor in the lives of 
many Indians of the Great Plains. The chase required many quick moves, and 
this helped to keep the family relatively small, the houses light and portable, 
and to restrict the personal equipment and household utensils to a few essential 
articles. Individual ownership of land was unknown among some of the tribes. 
Man was the exclusive breadwinner, and probably partly for this reason woman 
occupied a relatively low position. The mythology of the Indians was tinged by 
their hunting and military habits. The chiefs attained their positions because of 
their skill as hunters or warriors, and the organization of the tribes tended toward 
the development of an aristocratic type of government. With the disappearance 
of the buffaloes, the hunting tribes lost their chief support, and became dependent 
on the white man. Great numbers of buffaloes were killed as food for the con- 
struction gangs of western railroads, and for their hides, in great demand in the 
East for robes, belting for machinery, and other purposes. They practically dis- 
appeared from the southern plains in the middle seventies, and from the northern 
plains a few years later. 

The stock-raising industry of the Great Plains began in Texas and spread north- 
ward. Cattle were introduced into Mexico by the Spaniards about 1525, and before 
the Revolutionary War there were large cattle ranches north of the Rio Grande. 
In the middle 1850's, most of Texas was "a vast, unfenced feeding ground for 
cattle, horses, and sheep." At the close of the Civil War, cattle were very cheap 
in Texas, but brought high prices and were in great demand in the northern cities. 
As a result, the practice was developed of driving cattle northward in great herds 
to shipping points on the railroads that were then building across the Great Plains 
in Kansas and Nebraska. The "cow towns," as the shipping points were called, 
were established beyond the farming frontier, preferably where there was a good 
supply of water and grass. The business shifted west and south with' the advancing 
railroads, keeping in front of the farming zone. Some of the best known "cow 
towns" were Abilene, Newton, Wichita, Great Bend, Dodge City, and Hayes City 
(now Hays) , all in Kansas, and Ogallala, in Nebraska (Fig. 367). The banner year of 
the Texas cattle drive was 1884, when 4,000 men, equipped with 30,000 horses, drove 
1 ,000,000 cattle out of the state. Soon after, the drives were rendered unnecessary 
by the extension of railroads, which took the stock to market in much less time and 
usually in better condition. The stocking of the northern lands occurred, for the 
most part, after 1870, and before the close of another decade the business had 
spread to the Canadian boundary. For a time, large returns were realized from 
feeding cattle on the public grass. Many people accordingly entered the business, 



LIFE IN PLAINS 



497 




and in numerous places the range was overstocked and the pasturage injured. 
One result of this in many places was the introduction of sheep, which can live on 
pasturage which will not support cattle. The conflicting interests of cattlemen and 
sheepmen have caused much trouble in some of the grazing states, and have 
sometimes led to bloodshed. The development of the grazing industry on the 
Great Plains had an important influence upon the growth of the slaughtering and 
meat-packing industry in Kansas City, Omaha, St. Louis, Chicago, and (later) 
South Omaha, from which meat products were sent to the urban and industrial 
centers of the northeastern states and 
Europe. The number of cattle in 
Wyoming, for example, increased 
from n,ooo in 1870 to 521,000 in 
1880, in which year 60,000 were sent 
to Chicago and an equal number to 
Kansas City. During the same time, 
the number of sheep in Wyoming 
increased from 6,000 to 450,000. 

As the frontier of agricultural set- 
tlement pushed westward into the 
grazing area, the interests of farmers 
and stockmen were often at variance, 
giving rise to important legal prob- 
lems. Thus for a time cattle roamed 
at will, and the pioneer farmer had 
to fence his land to protect, his crops. 
In 1873, Texas solved this problem 

by passing a trespass law, under which the stockmen were held responsible for 
damage done by their animals to crops, even if the latter were not fenced in. 
This law facilitated the spread of the farming industry. Many of the cattlemen 
bought land and fenced it, or employed "line-riders" to watch their stock. Many 
who did the former, substituted sheep for cattle. Those unwilling to fence or 
line-ride, pushed away from the agricultural settlements into the Panhandle of 
Texas. These facts illustrate how conflicting uses of the land may acquire political 
significance, and how, in turn, legislation may affect the distribution of industries. 
They also afford an additional illustration of the chronic antagonism between 
pastoral and agricultural peoples (p. 495)- 

In 1880, the Great Plains west of the 98th or 99th meridian were occupied only 
by scattered stockmen, except along some of the larger valleys (Fig. 368). A few 
years later thousands of farmers moved to the High Plains, and began to grow 
wheat for export, using the seed and methods which they had employed farther 
east, where the rainfall is greater. The. population of Kansas increased 250,000 
between 1885 and 1888, largely in the western portion (Fig. 369). The agricultural 
invasion began because of heavy rains in the middle eighties, and was kept up for 
a few years by the advertising of railroads and the activity of town-builders and 
land-dealers. Then came several very dry years, and thousands were starved out 
of the region. Kansas lost some 200,000 people, and the western parts of Nebraska, 
the Dakotas, and the eastern part of Colorado were affected similarly (Fig. 370). 
Millions of acres returned slowly to grass, and within a few years the sites of hun- 
dreds of "cities" were marked only by parallel rows of cellar excavations, iron 



Fig. 367. Map showing principal 
'cow towns" of Kansas and Nebraska. 



498 



ELEMENTS OF GEOGRAPHY 



S.D. 



Net). 



._,._ Lf 



T€A. 



I |Under2persq.nu\ 

EEH2to6 " 
jgJU toia " 
H 18 and over 



hydrants at corners, and the like. Within the last few years, another agricultural 
invasion of the High Plains has been in progress. A series of unusually wet seasons, 
the activity of land companies, and the introduction of agricultural methods 
adapted to semi-arid conditions have been the leading causes. The outcome is 

still uncertain, but is not 
likely to be so disastrous as 
the first settlement, because 
men know better now how 
to make use of dry lands. 

The principal uses to 
which the semi-arid parts of 
the Great Plains will prob- 
ably be put in the future 
may be suggested briefly, 
(i) Farming by irrigation 
will be extended somewhat, 
but the greater portion of 
the higher plains appears 
to be non-irrigable because 
of insufficient water. The 
amount of water available 
from all sources constitutes 
but a small fraction of what 
would be required to irrigate 
all the land. There are gov- 
ernment irrigation projects 
on the Arkansas, Platte, 
Belle Fourche, and Missouri 
rivers (see Fig. 331). Much 
water is obtained from arte- 
sian wells in the Dakotas, 
and small artesian basins 
are known farther south. 
Ordinary wells also supply 
some water for irrigation. 
(2) "Dry-farming," espe- 
cially with hardy, drought- 
resisting plants (p. 276), 
promises much more than 
irrigation for the region as a whole. "Dry-farming" scarcely can be said to have 
passed the experimental stage, and howtlarge an area can be dry-farmed success- 
fully is quite uncertain. As already pointed out (p. 99), "dry-farming" seeks (a) 
to get the largest possible proportion of the rainfall to enter the ground, and 
(b) to reduce to a minimum the loss of water by evaporation from the soil. (3) 
Stock-raising, and stock-raising with subordinate farming, apparently must remain 
the dominant industries over large areas. 




Fig. 368. Fig. 369. Fig. 370. 

Figs. 368, 369, 370. Maps showing distribution 
of population on the western Great Plains in 1880, 
1890, and 1900. 



LIFE IN PLAINS 499 

Life in Arid Plains 

About Vs of the land is desert because of insufficient rain. By 
no means all dry deserts are plains; some are plateaus, and within 
desert plains and desert plateaus there may be ranges of high hills 
and mountains (p. 504), though these, in most cases, receive more 
rain than their surroundings. Many of the conditions of life are 
similar in arid plains and plateaus, and they are considered together. 
Life in cold deserts, such as Greenland and parts of the Arctic plains 
(pp. 507-508), differs greatly from that in dry deserts. Only the 
latter are considered here. 

The great deserts of the world occur in the zone of the trade- 
winds, or to leeward of high mountains. Their wide distribution 
and vast extent, the location of some of them near well-watered and 
thickly-settled regions, and the relations of their inhabitants to the 
latter, always have given them great importance in the life of the 
world. Save in the relatively small areas where irrigation can be 
practiced, or to which people may be attracted by valuable mineral 
deposits, deserts are doomed to have scanty populations. 

The power of mineral deposits to bring people to deserts is illustrated strikingly 
in the case of Nevada. Although the deposits first discovered there occurred 
beneath strips of land only a few hundred feet in width and in a most uninviting 
desert, they attracted thousands of miners and prospectors, and made Nevada a 
state in five years. Virginia City had a population of some 11,000 in 1880, and was 
a place of much importance. Later, the population of the city and state declined 
greatly (p. 473), but in the last decade it has increased again (81,000 in 1910) due 
to new discoveries of ore. Butte, Montana, a city of 39,000 inhabitants, is sup- 
ported largely by deposits of copper that underlie less than two square miles of 
arid land which, without the mines, could sustain only a few people. 

Plant life in deserts. Plants require water for growth, and 
they lose water chiefly by evaporation from their leaves. It is clear 
that, in general, plants with unusual ability to get and store water, 
and plants which lose but little water, are best suited to deserts. 
Most desert plants are provided with many long roots, which enable 
them to get more moisture from the dry soil than would be possible 
otherwise, and at the same time help them to stand against the 
winds, often of great strength. The loss of water is reduced by such 
things as thick skins, corky bark, and coats of hair. Some desert 
plants have no leaves, and some have only a few small, rounded, and 
fleshy leaves. Thus the loss of water by evaporation from leaf 
surfaces is prevented or diminished. Many desert plants have 



5oo 



ELEMENTS OF GEOGRAPHY 



thorns, spines, and unpleasant or poisonous juices, which help to 
protect them against devouring animals. Scattered shrubs and 
coarse grasses are among the leading types of desert vegetation. 
Figs. 371 and 333 show desert plants of various kinds. The plants of 
deserts have comparatively little economic value at the present time. 

After rain falls in the desert, many small, quick-growing plants spring up. 
Some of them bear bright flowers, and for a short time give the surface an appear- 
ance much in contrast with its customary barrenness. Soon they wither and die 
for lack of sufficient water. 




Fig. 371. View in the desert near Tucson, Arizona. 



The vegetation of oases (p. 504) is quite unlike that of the true 
desert. 

Animal life in deserts. Like certain plants, some animals 
have developed characteristics which help them to live in the desert. 
The severity of desert conditions is shown, however, by the small 
number and the small variety of animals which can endure them. 
Like desert plants, desert animals are, as a rule, scattered. Some 
are very fleet of foot, and thus are able to move between widely- 
separated watering places and to escape from their enemies. Some 
are slow-moving, but most of these are venomous, and all of them 
are able to go without water for long periods. A desert is an im- 
passable barrier to slow-moving animals which need water frequently. 
On account of the hot days and cool nights, many desert animals 
are more active during the night than during the day. Another 
characteristic of many desert animals is their dull color, not easily 
seen against the barren ground. 



LIFE IN PLAINS 



5oi 



The camel is the most important animal of the arid regions of the Old World, 
having long been called "the ship of the desert" (Figs.372and375). It is found in 
northern Africa and in Asia, from Arabia to China, and northward to northern Mon- 
golia. A draft camel carries 300 to 600 pounds, according to size, the customary 
load being about >£ the weight of the animal. It is said that caravans sometimes 
travel 20 out of the 24 hours at a steady gait of 2% to 3 miles an hour, halting 
only during the hottest part of the day. 

The camel is an excellent example of adaptation to environment. It has great 
endurance with a small supply of food and water; small nostrils, which can be closed 




■ ■- i^.c 1 . -.- '""":.:'i*«::y^"'",' _ .~jj>'' "*— :;-t '":-•'-'*■ 




-«&* 



Fig. 372. Part of a caravan in the desert. 

so as to prevent the entrance of the finest wind-driven sand; eyes protected against 
sand and sun by extremely long, heavy lashes; and peculiar padded feet, fitted for 
the hot sands. The parts of the body subjected most to heat and friction are 
protected by great callosities. When at rest in an oasis, a camel drinks only enough 
for the time being, but when on the march it makes provision for many hours in 
advance. At the end of a long march, a camel has been known to drink as many as 
20 gallons of water. During weeks of rest or light work, the hump increases in 
size; on long journeys, the material of the hump is absorbed into the system, 
maintaining the strength of the animal. 

Human responses to desert conditions. Agriculture is impos- 
sible in deserts, without irrigation, and few places have sufficient 
water for that. Furthermore, grazing in many cases is possible only 
along the margins of the desert, or in oases. Since deserts afford 



502 ELEMENTS OF GEOGRAPHY 

little in the way of food, they can support relatively few people, 
scattered widely in small groups. The conditions in deserts permit 
native tribes to make little progress in civilization. 

Along the borders of many deserts the conditions of life are a 
continuation of those in semi-arid grasslands (p. 494). The people 
wander from place to place with their flocks and herds, the size of 
the social group being determined by the supply of water and grass. 
In general, the people are scattered even more widely than in the 
steppe, for the smaller amount of rain means poorer pasturage. 
Along the margins of certain deserts, the people sometimes do a 
little farming when the water supply permits, in order to supplement 
the often uncertain and always restricted living afforded by their 
animals. As a rule, pastoral nomads view tillage with contempt 
and dislike, and in some tribes which plant crops, the work is done 
by the women only. 

We have seen (p. 500) that deserts may support considerable vegetation for a 
short time after rain falls. Along the edges of certain deserts, pasturage is available 
in the wet season, where the surface is bare in the dry season. This may control 
the seasonal migrations of pastoral tribes. In winter, the Arabs find scant pas- 
turage for their goats and sheep on the northern border of the Sahara; in summer, 
they drive them to the slopes of the Atlas Mountains. In the same way, flocks 
and herds are driven at various points into the southern edge of the Sahara in 
summer, which is there the rainy season. 

The arts of desert people are primitive and confined largely to 
household industries, for raw materials are few, and the wide disper- 
sion of the people prevents much division of labor. Making leather 
and leather utensils from the skins of animals, pottery from clay, 
and blankets and rugs from wool furnished by the flocks, are typical 
industries. 

Among American Indians, the potter's art was developed best in the arid 
Southwest. Here water was at a premium, and durable, water-tight vessels an 
absolute necessity. Perhaps* the manner in which clay is hardened and baked by 
the desert sun when exposed by the evaporation of temporary pools of water, and 
along the courses of withering streams, gave the needed suggestion to the early 
inventor. 

The Navajo Indians of the Southwest possess large flocks of sheep, and derive 
a considerable income from the sale of wool and blankets. The latter are made by 
the women in many artistic designs, and enjoy a wide reputation. It is said that 
the pastoral and industrial habits of the Navajos date from their theft of a flock 
of sheep from early Spanish settlers along the Rio Grande. 

From force of necessity, most wandering desert tribes are rob- 
bers and marauders. They pillage caravans and hold travelers for 



. 



LIFE IN PLAINS 503 

ransom, or exact heavy tolls in return for safe passage through the 
desert. They raid adjacent agricultural lands, and in some cases 
have levied regular tribute upon them, or have conquered and 
settled in them. The Sudan and Egypt have been invaded 
repeatedly by tribes from the Sahara. Where conquering people 
from the desert have adopted a sedentary life in 'more favored 
districts, they have sooner or later lost the warlike spirit and 
many of the other traits bred by the desert. This was illustrated 
by the Arabs (Moors) who settled in Spain, following their conquest 
of that country. 

The inhabitants of deserts are excluded more or less completely 
from the culture of the outside world. Hence, as in mountains 
(p. 471), old manners and customs persist. Customs of the time 
of Christ still are observed by the inhabitants of the desert of Arabia. 
Scattered widely in small groups, desert people develop many dia- 
lects. They are compelled to eat very sparingly of the few things 
available. It is said that an ordinary European meal for one person 
would suffice for six desert Arabs. Nothing is wasted; the Tibbus 
of the Sahara eat even the skins and powdered bones of their dead 
animals. Their small food supply has led various tribes to check, 
in different ways, the growth of population. The scanty diet and 
severe hardships incident to life in the desert help to produce a 
distinct physical type. The men are prevailingly thin, but wiry, 
and capable of great exertion. Desert scenery is, in general, monot- 
onous; therefore desert nomads have acquired unusual powers of 
observation and a remarkable sense of locality. Intellectual activity 
necessarily is restricted in the desert. The dull monotony of the 
environment and the lonely life tend to lead the mind into reverie 
and contemplation. The majesty of the larger deserts, their seemingly 
endless extent, their great dust and sand storms, and the precari- 
ous position of man, all tend to inspire feelings of awe and reverence. 
It is significant that Christianity and Mohammedanism were associ- 
ated closely in their origin and development with the arid and semi- 
arid regions of the Old World. 

Life in oases. In deserts, permanent settlements based on 
agriculture are possible only in oases, where there is water supplied 
by springs, artesian wells, or rivers. The source of the water supply 
may be outside the desert in well-watered regions, or within the 
desert where elevations rise high enough to compel the passing 
winds to give up a part of their moisture. 



5°4 



ELEMENTS OF GEOGRAPHY 



The Nejd Plateau, in the heart of Arabia, rises to an elevation of more than 
5,000 feet, and here there are fertile oases, cultivated for centuries, and extensive 
pastures. Even in the Sahara, there are a few mountains which receive rainfall 
sufficient to support trees (Fig. 373). The streams formed on these mountain 
slopes disappear after descending to the surrounding desert. Some of the narrow 
valleys are farmed, and grazing is possible over larger areas. In order to encourage 
the settlement of wandering and troublesome tribes, the French have made many- 
oases by sinking a great number of artesian wells in the northern Sahara, south of 
the Atlas Mountains. The water is obtained from sloping beds of porous rock 

which extend out beneath 
the desert from the moun- 
tains. 



Some oases serve 
merely as headquarters 
for tribes which roam 
over the surrounding 
desert in search of pas- 
turage, and of caravans 
which they may attack. 
Some support towns, 
most of which are 
small. In general, the 
larger ones are located 
on the main caravan 
routes, where there is 
better opportunity for 
trade (p. 505). The houses in many cases are built of stone or 
adobe (sun-dried clay). In many cases, oases are cultivated most 
carefully in order to secure the largest possible returns from the 
restricted area which can be watered. Vegetables, cereals, and 
fruits, especially dates, are grown in the oases of the Sahara and 
the deserts of southwestern Asia. 




100 200 



Miles 'TOS 



*S^ 



*^S» 



ft 



Fig- 373- The mountains of Tibesti, in the 
Sahara. Streams from the mountains wither and 
disappear in the surrounding desert. 



The date palm has a trunk in some cases fifty to sixty feet in height, ending in 
a great crown of feathery leaves (Fig. 374). Bearing trees average from 100 to 
200 pounds of dates a year, though yields of 500 or 600 pounds have been known. 
A tree may bear fruit for a century. The date palm is adjusted perfectly to 
conditions in the oases of low-latitude deserts, for it requires a very dry, hot 
climate, and a moist soil. It has been said with truth that the Arabs built 
their lives on the date palm. It was introduced into Spain by the Saracens, 
and brought by the Spaniards to Mexico and southern California, where it is 
an important decorative tree, but rarely bears fruit. In the future, it probably 
will have commercial value in the irrigated lands along the lower Colorado River 
(P- 373)- 



LIFE IN PLAINS 



505 



Oases in deserts are not in most cases such delightful gardens as 
often described, although in striking contrast with the barren desert 
about them. They are subject to frequent sand-storms, their water 
supply is small and in many cases impure, and their products are 
restricted in variety and 
in quantity. Nor are 
habitable oases numer- 
ous under natural con- 
ditions. The number 
of habitable places (in 
effect oases) in certain 
deserts has been in- 
creased by artesian 
wells (p. 504), the stor- 
age and diversion of 
stream waters, etc. 

The oases of the Souf 
lie in the hollows among im- 
mense dunes in the Algerian 
Sahara. The date gardens 
of these oases are contin- 
ually in danger of being 
buried by sand, for the air is 
in motion almost constantly, 
and even a gentle breeze 
starts clouds of fine sand. 
After every severe wind- 
storm, the natives toil for 
days carrying the sand in 
baskets out of the gardens. 
In summer, when the tem- 
perature in the shade may 
reach 120 F., this work is 
done largely at night. 

Fig. 374. Date palms loaded with fruit, 

Commerce Of the Biskra, Algeria. 

desert. Where a desert 

lies between well-watered and populous regions, important trade may 
be carried on across it. Some trade is carried on also between agri- 
cultural lands and the borders of neighboring deserts, because of their 
contrasted resources and the desire of the desert people to supple- 
ment their meager products. Timbuctoo, on the Niger River, and 
Damascus, in Syria, are examples of places which serve as gateways 









"«% 




506 



ELEMENTS OF GEOGRAPHY 



to deserts. The former is said to be visited each year by 50,000 to 
60,000 camels. One of the few occupations of the desert is that of 
driving camels and leading caravans. Mohammed himself was a 
caravan leader. 

For centuries, goods were carried in large quantities across the vast deserts of 
central and western Asia only by pack animals, especially the camel, and even to-day 
this is the case over most of the region (Fig. 375). A number of caravan routes cross 
the Sahara, extending from oasis to oasis. The trade which originates or terminates 
in the Sahara is largely in dates, salt, clothing, cereals, and camels, while for centuries 




Fig- 375- Camels in northwestern India. A portion of a caravan which has 
come through Khyber Pass from Afganistan. 



the through trade has included such things as ivory, gums, spices, and gold dust. 
Prince Henry of Portugal learned of the trans-Saharan trade while on an expedition 
against the Moors in northern Africa in 141 5, and partly with the idea of diverting 
the trade of the Guinea Coast to his own country by water, he began the long series 
of explorations along the coast of Africa which culminated in the discovery of the 
all-water route to India. The use of the latter route to the East injured greatly 
the caravan trade across Asia. A trans-Saharan railroad is now projected. 

Political conditions in deserts. The hard conditions of life 
in deserts repeatedly have driven their inhabitants out to conquer 
other regions (p. 503). On the other hand, the conquest of deserts 
from without always has been attended by great difficulties, and in 
some cases never has been accomplished. The love of freedom and 
the fighting ability characteristic of desert peoples, in addition to 
the difficulties which an invading army finds in the lack of roads, 
water, and food, have helped to produce this result. Furthermore, 
the scant resources of deserts have made them relatively uninviting 
to outside people. 



LIFE IN PLAINS 507 

The great body of the people of Arabia and of the Sahara are still free. France 
has undertaken the control of the latter to secure safe communication between her 
possessions to the north and south of the desert. 



Life in Arctic Plains 

The plains which border the Arctic Ocean are known as barren 
lands in North America, and as tundras in Eurasia. They form a cold 
desert, snow-covered for some two-thirds of the year. The short sum- 
mers, low temperatures, and cold or frozen soil prevent agriculture, 
and restrict vegetation chiefly to stunted bushes, mosses, and various 
quick-growing, flowering plants. The few, widely scattered inhabit- 
ants of the tundras depend largely on their herds of reindeer and on 
hunting for their living. Fishing is an important occupation during 
the three or four months when the streams are free from ice. A 
nomadic life results from the necessity of following the game and 
the reindeer herds, which wander half-free in search of pasturage. 
As in the steppes and dry deserts, this nomadic life means small, 
easily transported dwellings — in many cases a tent consisting of a 
framework of poles covered with skins — and few and simple house- 
hold utensils. Some of the tribes move northward with their herds 
in the summer, and return to pass the winter in the forests which 
border the tundras on the south. Here the timber affords some 
shelter, fodder is available for the reindeer, and game may be hunted 
for food and fur. 

All that the camel is to the inhabitants of low-latitude deserts, the reindeer is 
to the men of the Arctic desert. It is indifferent to cold, lives on reindeer moss, is 
an excellent draft animal (Fig. 376), and its milk constitutes an important item 
of food. Its flesh is used for food; its bones and horns afford material for making 
various implements; its tendons and sinews serve for thread; and its skin is used 
for shelter and clothing. The reindeer is the most desirable form of wealth on the 
tundra. In some places, a herd of 50 head, which will support one family of four 
or five members, requires between 4 and 5 square miles of tundra pasturage. 
This means at best a very sparse population. 

Some years ago the United States Government imported nearly 1 ,300 reindeer 
from Siberia, for the benefit of the natives of northern Alaska. The herds have 
increased rapidly, and are proving of great value. 

The Athapascan Indians of the Arctic Coastal Plain of Canada 
are among the most primitive of their race. They lead a preca- 
rious and difficult existence, depending of necessity on hunting and 
fishing. 



5 o8 



ELEMENTS OF GEOGRAPHY 



The cold of the Arctic plains permits little progress. Life is a 
constant struggle to secure food, clothing, and shelter. There is 
little opportunity for trade. Situated upon the outskirts of the 
inhabited world, the frozen deserts of the north have played a much 
less important part in history than the centrally-located deserts 
of lower latitudes. Nor does it seem likely that they can become 
of much importance in the future. 




Fig. 376. Reindeer and sledge. 



Life in Humid Plains of Low Latitudes 

Near the equator, the climate of the lowlands is characterized 
by heavy and frequent rains, and by high, nearly uniform tempera 
tures throughout the year (p. 160). As we have seen, this results 
in a dense, varied vegetation (Figs. 377 and 378), such as that con- 
stituting the forests of the Amazon and Congo valleys. The dis 
tinctive life of humid plains in low latitudes is therefore that of 
the tropical forest, or jungle. In some of the other realms which 
we have considered, man has been handicapped by lack of useful 
vegetation. Here, the very abundance of plant life is an obstacle 
to progress. 

Response of natives to conditions in tropical forests. The 
dense forests of equatorial regions are occupied by relatively sparse 
populations of backward natives. The high temperatures and 
the moisture are enervating, and continued exertion is difficult. 
The climate has encouraged indolence and shiftlessness until they 



LIFE IN PLAINS 



509 



have become leading characteristics of the natives. The luxuriance 
of the natural vegetation makes the clearing of land difficult, and 
even where it is cleared, a constant struggle is necessary to keep 
back the encroaching plants. Unused trails through the forest 
are obliterated quickly, and all trace of settlement soon disappears 
from abandoned clearings. Under these conditions, it is not strange 




Fig. 377. Tropical forest and river in flood. Southern Mexico. (W. L. 
Tower.) 



that agriculture rarely is practiced. An indolent people will not 
undertake hard work when this is unnecessary. Throughout the 
world, man appears to have developed agriculture, or to have domes- 
ticated animals, generally only when the natural food supply became 
too small. In the equatorial forest, there is an abundant natural 
food supply. The natives live chiefly on the fish afforded by the 
many rivers, and such game as inhabits the forest. This is supple- 
mented in many places by the products of certain plants, such as 
the sago palm. 

The large animals found in many places in the open country adjacent to the 
tropical forests penetrate the latter only a short distance. They come and go 



5io 



ELEMENTS OF GEOGRAPHY 






through the denser growth by paths which they keep open by frequent passing 
(Fig. 378). Well within the forest, there are few sources of food for animals near 
the ground. Flowers and fruits are found in the tree tops, however, and hence 
animal life is represented chiefly by flying and climbing forms, such as insects, 







Fig. 378. View showing plants of various kinds in a tropical forest, 
through the forest shows at the right. Southern Mexico. (W. L. Tower.) 



Path 



LIFE IN PLAINS 



5ii 



birds, snakes, and monkeys. Many of the birds and snakes resemble the foliage 
in color, a fact which favors concealment. 

Little is needed by the inhabitants of the tropical forest in the 
way of clothing and shelter. Some of the lowest savages have no 
homes. Some of the people live in floating houses on the rivers, 
which constitute the most important lines of travel through the 
forest, or in huts built on piles, in order to escape the floods. 

Agriculture has been developed in a small way in clearings near 
the edges of the equatorial forests. In some cases, this consists in 




Fig. 379. Pygmy village in the Congo forest. 



scarcely more than planting crops, and leaving them to grow. Bana- 
nas, bread fruit, rice, and other things are grown in different places, 
chiefly by the women. Very little labor brings large returns, and 
thus steady effort is discouraged. As in the equatorial forest gener- 
ally, life is too easy; there is no spur to progress. 

The Pygmies who inhabit parts of the Congo forest represent perhaps the 
lowest type of human betngs. The average height of the adults is said to be only a 
little more than 4 feet, and many are shorter. They make no attempt at farming, 
but live by hunting and fishing. They kill small game with arrows and spears 
tipped with a poison made from certain plants, and capture even large animals in 
covered pitfalls which they construct in the narrow runways followed by the 
animals (p. 509). They catch fish in nets or baskets, sometimes stupefying them by 
putting in the water the powdered fruit of a palm. They live in small, scattered 
groups where there are openings in the undergrowth (Fig. 379), building tempo- 



5 i2 ELEMENTS OF GEOGRAPHY 

rary huts consisting in many cases of flexible sticks covered with leaves, and shifting 
from spot to spot in quest of game. They carry on some trade with other tribes, 
bartering meat, skins, and plant poisons, for weapons and vegetable food. The 
Pygmies have no arts save those noted in connection with their hunting and 
fishing; no family ties; no traditions of their ancestors; and, it is believed, no idea 
of a future state. 

Commerce of tropical forests. The forests of tropical low- 
lands furnish products of much importance to the outside world, 
such as ebony, mahogany, rubber, gums, palm-oil, and copra. Trade 
follows the waterways, and in general those sections are most favored 
commercially which are situated conveniently with reference to a 
navigable river (p. 165). 

The humid lowlands of the tropics are of far greater importance 
to man than the Arctic plains, but unfortunately the settlement and 
development of them by people from middle latitudes are attended 
with great difficulty (pp. 157-158). 



Questions 

1 . (1) How might one prove that a given coastal plain was formerly a marginal 
sea-bottom? (2) How might one determine whether such a plain became land by 
rise from beneath the sea, or by lowering of the surface of the sea? 

2. By what are the characteristics (topography, fertility, etc.) of any given 
plain determined? 

3. Why are the soils of most plains thicker and more fertile than those of 
plateaus and mountains? 

4. (1) What great plains, now of little value to man, are likely to have greatly 
increased importance in the future? Why? (2) What ones are likely to continue 
of little significance? Why? 

5. What are the principal factors which influence the value of semi-arid land 
f or " dry-farming " ? 

6. Compare and contrast the life of primitive peoples in arid deserts and rugged 
mountains. 

7. How does the life of people in Arctic regions resemble that of desert tribes 
in lower latitudes? 

References 

Herbertson: Man and His Work, Chs. I, III, IV, V. (London, 1908.) 

Johnson, W. D.: The High Plains and Their Utilization, in 21st Ann. Rept., 
U. S. Geol. Surv., Pt. IV, pp. 601-741. 

Libby: Physiography as a Factor in Community Life, in Jour, of Geog., Vol. 
VI, pp. 209-214. 

Mill: Development of Habitable Lands, in Jour, of Sch. Geog., Vol. IV, pp. 
161-170, 218-223. 



LIFE IN PLAINS 513 

Nimmo: The Range and Ranch Cattle Business of the United States; House Ex. 
Doc. 267, 48th Cong., 2d Sess. 

Platt: Climatic Control in the Desert, in Jour, of Sch. Geog., Vol. IV, pp. 
255-264, 281-286. 

Powell: Physiographic Features, in Physiography of the United States, pp. 
33-64. (New York, 1895.) 

Powell: Physiographic Regions of the United Slates, Idem, pp. 65-100. 

Semple: Influences of Geographic Environment, Ch. XIV. (New York, 1911.) 

Widtsoe: Dry-Farming. (New York, 191 1.) 



CHAPTER XIX 
COAST-LINES AND HARBORS 

Importance of coast-lines. There is great freedom of move- 
ment over the ocean. A ship may sail direct from one port to another 
thousands of miles away (Fig. 113), or it may make a roundabout 
voyage, calling at intermediate ports on the way. A modern steam- 
ship can carry ten to twenty train loads of freight in a single cargo, 
and it costs far less to operate one steamer than to run ten or twenty 
trains. Furthermore, trains call for the maintenance of a railway, 
which is very expensive. Hence the carriage of freight by rail is 
much more expensive than by boat. The cheapness of ocean trans- 
portation makes it possible to carry enormous quantities of relatively 
low-priced freight, such as cereals, lumber, and raw materials of all 
sorts, from one part of the world to another. Modern commerce, 
therefore, depends much on the ocean highway (Figs. 114 and 115), 
but it owes its rapid development in part to favorable coast-lines 
through which access to the sea is secured. 

The prosperity of some countries depends largely on commerce. 
Holland, for example, at the mouth of the Rhine, is situated favorably 
for sea trade, and through its commercial activities Dutch influence 
has been extended to many parts of the earth. Countries like 
Bolivia and Switzerland, shut off from the sea, have been more 
limited in their influence. Countries with an unfavorable sea-coast, 
like Austria, or with but small extent of coast-line, like China, are 
handicapped when compared with a country like the United States, 
with fairly good coasts on three sides. 

Successful commercial voyages from one continent to another 
require skill in navigation. In early days, seamanship was much 
influenced by the character of the coast-line. It was unsafe to 
venture far from land, for vessels were small and there was no way 
of determining position accurately, or of reckoning distances. Hence 
seamanship developed first along the shores of quiet inland seas 
like the Mediterranean, or where deep bays and sheltering islands 

5H 



COAST-LINES AND HARBORS 



SiS 



invited ventures from one headland or island to another, as in Nor- 
way. Thus the first nations to become sailors, fishermen, explor- 
ers, and sea traders were influenced by the nature of their sea-coasts. 
With modern steamships and a highly developed science of 
navigation, voyages are undertaken readily to distant parts of the 
earth. But even the giant steamship needs safe anchorage in quiet 
waters while its cargo is being received or discharged. In some 
cases, ocean commerce is carried on from places which have no 




Fig. 380. Map showing regular outline of newly elevated coast. Dotted 
lines indicate contours; interval 25 feet. (Nome, Alaska, Special Sheet, U. S. 
Geol. Surv.) 

harbor. In such cases, vessels anchor off shore while the cargo 
is carried (lightered) from them to shore, or from shore to them, 
in small boats. During heavy seas lightering is impossible, and 
many wares cannot be handled to advantage in this way at any 
time. Hence, other things being favorable, coast-lines with deep 
bays and good harbors are natural centers of seafaring activities, 
as in early days. 

Characteristics of coast-lines and their origin. If land along 
a coast were to be elevated or the sea-level lowered, a portion of 
the sea floor would be exposed. The sea floor is generally smooth 
and even. Hence the emergence of a coastal strip tends to produce 
an even, regular shore-line (Fig. 380) fronted by shallow water. 
Coasts which have risen recently, relative to sea-level, are without 
good harbors, except where some large river, flowing across the 
coastal plain, offers a haven at its mouth. 



516 ELEMENTS OF GEOGRAPHY 

Commerce with such a coast is handicapped severely. Large 
vessels must anchor off shore while their cargoes are lightered, unless 
artificial harbors have been provided by the construction of break- 
waters, jetties, or long quays. The east coast of India, most of 
the Gulf coast of Mexico, and much of the west coast of South 
America present these conditions. Madras and Vera Cruz have 
artificial harbors, because the demand for a commercial outlet from 
an important region justified the great expense involved in making 
a harbor. The coasts of most tropical lands are more regular than 
those of higher latitudes, and this has helped to retard the develop- 
ment of tropical regions. 

The submergence of a coast land having hills and valleys pro- 
duces a new shore-line which is irregular (Fig. 381). The drowned 
valley bottoms form bays, while the inter-valley ridges stand forth 
as headlands. Isolated hills on the old lowlands may front the 
new coast as islands. Such a coast-line commonly has many shel- 
tered bays and harbors. Deep water is likely to be found over the 
submerged river channels, and may extend many miles up the drowned 
valleys, making it possible for vessels of moderate draft to go far 
inland. Thus the drowned lower portion of the Hudson has a 
minimum depth of 11 feet for more than 150 miles. 

Commerce is favored by the irregular coast of a newly sunken 
land area. Most important commercial ports, such as the Atlantic 
ports of North America and Europe, are along depressed coasts. 
The chief sea fisheries, also, are associated with irregular coasts, 
partly because of the many convenient refuges for fishing fleets. 
Not infrequently, also, large bays, like Chesapeake Bay, support 
valuable shore fisheries. In some places, as along parts of the 
Atlantic coast from Chesapeake Bay to Maine, irregular coasts 
afford more good harbors than commerce needs, and many of them 
are used only by small fishing fleets. 

Where an irregular coast-line is produced by the sinking of a 
coastal plain, the bays may be wide (Why?), like Delaware and 
Chesapeake bays, but most of them are shallow, except along the 
line of the old river channel, and they may have marshy land along 
their borders. Few places on the shores of such bays are suitable 
for the development of a great port. Where a higher, more rugged 
region is submerged, the bays are likely to be narrow and fiord- 
like, as in Alaska and Norway. Most of them are deep, and some 
are bordered by high land which rises so abruptly from the water 



COAST-LINES AND HARBORS 



5i7 



that no room is available for a city. Where the ocean finds access 
to an interior valley, a long inland arm of the sea, like Puget Sound, 
is developed. The sheltered inner route from Puget Sound to 
Alaska is perhaps similar to Puget Sound in origin. A former moun- 
tain pass in the Coast Range, now submerged, forms the picturesque 
Golden Gate entrance to San Francisco harbor (Fig. 382), and a 




Fig. 381. Map showing irregular outline of a depressed coast. Dotted lines 
indicate contours; interval 20 feet. (Monhegan, Maine, Sheet, U. S. Geol. Surv.) 



little further sinking would change much of the central valley of 
California into a great, sound. 

The modification of shore-lines. All shore-lines are subject 
to constant changes by waves, shore and tidal currents, rivers, 
winds, and ice. 

The effect of glaciers on shore-lines has been noted (pp. 393, 398). 
Parts of the coast of New England have been modified in this way. 
Much of the value of Boston harbor depends on the protection 
afforded by islands of glacial origin. Shore ice has little effect on coast- 
lines, but is a serious obstacle to navigation along some coasts (p. 381). 



5i» 



ELEMENTS OF GEOGRAPHY 






Winds often make dunes on the sea shore (p. 314), and the dunes 
may afford the land some protection from the sea, as along the coast 
of Holland, but they rarely change the outline of the land to any 
great extent. The action of the wind in producing waves and cur- 
rents is much more important. 

Rivers affect shore-lines but little through erosion, but delta- 
building rivers may change the outline of the land greatly (p. 374). 




Fig. 382. Diagram showing arm of ocean formed by invasion of valley through 
a submerged sag in mountain range. San Francisco harbor. Dotted lines indi- 
cate bar across entrance. (U. S. Coast and Geod.Surv., Chart No. 5500.) 

Other things equal, delta lands grow most rapidly in the quiet waters 
of inland seas and bays. Thus the delta of the Mississippi (Fig. 
259) extends into the Gulf as a great irregularity, with many smaller 
irregularities about its borders. Delta-building in bays may lessen 
the irregularities of the coast, by filling the indentations. Thus 
most bays entered by large streams are made shallower constantly 
by the deposition of river sediments. The value of Mobile Bay is 
lessened in this way, and many others, especially about the Mediter- 
ranean, which were important centuries ago, are now partly or 
entirely filled. The city of Adria, Italy, once the port for the mouth 



COAST-LINES AND HARBORS 519 

of the Po, is now fourteen miles from the coast, and the Rhone delta, 
building forward at the rate of 200 feet a year, has changed the 
coast-line so rapidly that it has never developed an important 
port (p. 415). 

On exposed coasts, delta-building is less rapid (Why?), and pro- 
duces fewer irregularities than in partially enclosed waters. The 
delta of the Amazon, 
for example, does not 
project beyond the gen- 
eral coast-line. Delta 
lands are low, marshy, 
and subject to floods, 
while the indentations 
of their borders are 
shallow, and, in most 
cases, subject to de- 
position. For these 
reasons, they are 
poorly suited to the 
development of ports, 
and except at the 
mouths of great rivers, 
like the Mississippi and 
Amazon, deltas rarely 
become the sites of 
important commercial 
centers. 

Waves and currents are the chief agents which modify coast- 
lines. On irregular coasts, the general tendency of waves is to wear 
away headlands (Fig. 383) and fill bays, thus making the shore more 
regular. On regular coasts, their general tendency is to wear back 
the shore-line. Waves and currents therefore tend to destroy 
harbors. In many cases serious interference with commerce is 
prevented only through costly operations in the protection and 
improvement of harbors. 

Waves are at work almost constantly on some part of every 
coast-line. Large waves are more powerful than small ones; hence 
wave work is influenced largely by the winds. Coasts exposed to 
stormy seas are affected more than those in quiet waters, and those 
of loose material, such as gravel and sand, are attacked more effective- 




land. 



Fig. 383. Wave erosion of an exposed head- 



520 ELEMENTS OF GEOGRAPHY 

ly than those of solid rock. Along the eastern coast of the United 
States, the unconsolidated sediments of the coastal plain, and the 
glacial drift of parts of New England, permit more rapid changes 
than are possible on a rocky coast, like that of Maine or Norway. 

Wave action varies according to the nature of the coast and 
the depth of water. In deep water away from shore, the water in 
a wave does not move forward. An idea of its motion may be gained 
from a field of waving grain, where wave after wave crosses the 
field, though each moving stem is fixed to the ground. Again, if 
one end of a long piece of rope is fixed, while the other end is shaken 
up and down, successive waves travel from the end shaken to the 




Fig. 384. Diagram to illustrate the movement of water in waves. The small 
circles represent the movement of water particles. 

end which is fixed. Both the grain and the rope come to rest finally 
just where they started. The curved line of Fig. 384 represents 
the crest and trough of a wave (the undulating ocean surface) where 
the water is deep, while the circles show the path of a particle of water 
in the wave. The motion of the water in a wave is greatest at the 
surface, and diminishes rapidly downward. For this reason, waves 
have little or no effect on the ocean-bottom in deep water. 

When a wave advances into shallow water, its motion changes, 
for the movement of the water in the lower part of the wave is hin- 
dered by friction against the bottom. The top tends to pitch for- 
ward, making surf (Fig. 385). A somewhat similar effect may 
be produced in deep water, when winds blow forward the tops of 
waves, forming whitecaps. Hence during storms, and especially 
in shallow water, there may be a distinct forward movement of 
the water in a wave. But generally in deep water it is only the 
wave motion, not the water, which travels forward. If the water 
moved forward with the wave, the ocean would be hardly navigable, 
for in many cases the forward motion of the wave is as fast as the 
forward motion of a steamer. 

In shallow water, the water which is thrown forward against 
the shore runs back down the slope of the bottom as the undertow, 
so dangerous to bathers on many coasts. Drownings have resulted 
so frequently from bathers being caught by the undertow that many 



COAST-LINES AND HARBORS 



521 



bathing beaches now have regular life guards constantly on watch 
during the bathing hours. This forward and backward movement 
of the water is able to effect much erosion, if the movement is vigorous 
and the waves are well supplied with tools. 

If waves reach the shore obliquely, they produce a movement 
of water parallel to it. Such a movement is known as a shore or 
littoral current. Where a shore is exposed to prevailing winds 




Fig. 385. Surf wave at Point Buchon, California. 



from one quarter, the resulting shore currents are constant in direc- 
tion. Littoral currents are most important in moving the material 
worn from the land by waves. 

Erosion by waves. The force of waves hurled against the 
shore may be very great. Surf has .been thrown to heights of more 
than 100 feet with force enough to destroy lighthouses. The strength 
of waves on the coast of Great Britain is sometimes as much as 
three tons per square foot, and the average for winter waves is said 
to be about one ton per square foot. Such waves are able to move 
masses of rock weighing several tons. During one storm more than 
200 blocks of concrete, weighing 4 tons each, were swept from the 
breakwater at Cherbourg, France, and tossed over an embankment. 
It is clear, therefore, that the force of waves is great enough to wear 
shores, even of solid rock. Where deep water is found near shore, 
as along most precipitous coasts, erosion depends on the work of 



522 



ELEMENTS OF GEOGRAPHY 




Fig. 3 86 . Cliff showing undercutting by waves ; 
Kelleys Island, Lake Erie. (H. E. Wilson.) 



the water alone. Where waves break in shallow water, pieces of 
rock may be hurled forward with the rushing water, and serve as 
powerful tools to cut away exposed cliffs. In severe storms, cliffs 

are, in rare cases, driven 
back many feet in a 
few hours. The waves 
of lakes are never so 
strong as the great 
waves of the sea 
(Why?), but the storm 
waves of large lakes 
have great force, and 
sometimes wash away 
piers and breakwaters, 
even in a single storm. 

The existence of so 
great a force as that 
of waves on an exposed 
coast has led to many 
attempts in different countries to use wave power for practical 
purposes. None of the devices yet tried has proved practicable on 
an important scale. A chief obstacle is the extremely variable 
character of the waves. 

Where waves erode the land they make steep slopes, or cliffs. 
As waves cut away the base of a cliff (Fig. 386), the upper part may 

slump. In this way the cliff 
recedes more rapidly, and more 
material is supplied for the 
waves to hurl against the cliff 
base. 

Cliffs developed by wave- 
cutting are bordered by wave- 
cut terraces a little below the 
surface of the water (Fig. 387). 
The width of such a terrace 
measures roughly the advance 
of the water on the land by the cutting of its waves. By rise of the 
land, or by sinking of the sea, the terrace may become land (Fig. 388). 
By driving back sea cliffs, waves tend to increase the ocean area 
at the expense of the land. The island of Heligoland, off the German 




Fig. 387. A cliff fronted by a terrace. 
Outer (dotted) part of terrace built by 
deposition of sediment; inner part due 
to wave cutting. 



COAST-LINES AND HARBORS 



52.3 




Fig. 388. Wave-cut terraces now well above 
the sea, indicating relative change in level of land 
and sea. Seward Peninsula, Alaska. 




Fig. 389. Diagram to represent a low sea cliff. 



coast, has been reduced by wave action to less than one-twentieth 
of its area a thousand years ago. Numerous shoal areas off the New 
England coast are due 
to the complete re- 
moval of small islands. 
Where land near the 
coast is high, a 
well-developed cliff 
may interfere with com- 
munication between 
the sea and the inte- 
rior. Where the coast 
land is low, sea cliffs are 
unimportant (Fig. 389). 
Deposition by 
waves and shore cur- 
rents. Material worn 
from the land by 
waves, or brought to 
the shore by rivers, is shifted about by waves, undertow, and shore 
currents, but finally comes to rest. If left at the shore-line it makes 
a beach (Fig. 390). If 
carried farther out into 
the water, it takes on 
other forms. Fine par- 
ticles of mud generally 
are carried out into 
deeper water, while 
coarser material, such 
as sand and gravel, 
make the beach. 

Waves may build 
reefs or barriers a 
little out from the 
shore. They are de- 
veloped near the line 
of breakers, where the 
incoming wave leaves 

much of the sediment which it is moving toward the shore. The 
undertow may contribute sediment to the reef by carrying it out 




Fig. 390. Wave-cut cliff with some of the mate- 
rial left in the form of a beach. Lake Michigan. 



5 2 4 



ELEMENTS OF GEOGRAPHY 




Fig. 391. Diagram representing a 
cross-section of a barrier beach. 



from the shore. There are several such reefs along some coasts, 
parallel to one another and to the shore. They are, in some cases, 
troublesome to navigation, especially where they make shallow water, 

or "a bar," at the entrance to 
a harbor. 

Waves may build the crest 
of a reef above water, convert- 
ing it into land (Fig. 391). By 
building dunes, the wind may 
then aid in raising the surface still higher above the water-level. This 
seems to have been the origin of many low, narrow belts of sandy 
land parallel to coasts, with marshes and lagoons behind them (Fig. 
392). Such barriers are formed only in shallow water. They are 
common off low coastal lands, for off most such coasts the water is 
shallow. This type of shore is illustrated at many places from New 
York to Texas. The coast-line produced by the reefs is more regular 

(as a rule) than that 
of the mainland be- 
hind them. Lagoons 
enclosed behind reefs 
provide harbors in some 
places where otherwise 
they would be lacking. 
In time, wave action 
may cause such coast- 
lines to recede even be- 
yond the original line 
of the mainland. 

Where a shore cur- 
rent reaches a bay, it 
does not, as a rule, fol- 
low the outline of the 
bay, but tends to cross 
it in the direction in 
which it was previously moving. Under such circumstances it may 
build an embankment or spit of gravel and sand near the entrance to] 
the bay. Currents do not build spits above the water, but waves 
may build them up into land by washing material from their slopes 
up to their tops. After they become land, the wind may build dunes 
upon them (Fig. 395). When spits (Fig. 393) cross bays they become 




Fig. 392. A curved barrier beach enclosing a 
lagoon; Gilbert Lake, near Brainerd, Minn. 



COAST-LINES AND HARBORS 



525 



bars. Along some coasts, as on the south side of Martha's Vineyard 
Island, such bars have closed the entrances to many bays. 

Reefs, spits, and the land to which they give rise, increase the 
irregularity of the coast-line for a time; but they represent the first 
step toward regularity, for, after the reefs have become land, the 
lagoons behind them are likely to be filled with sediment washed 
down from the land or 
blown in by the wind (Fig. 

394). 

Deposits of gravel and 
sand are sometimes made 
between a mainland and 
islands near it. Nahant 
Island, on the coast of 
Massachusetts, and the 
Rock of Gibraltar, on the 
coast of Spain, have been 
thus "tied" to the main- 
land. 

Bars and reefs often 
hinder the movements of 
vessels, especially when 
they tend to close the en- 
trances of harbors. A spit 
which does not obstruct 
the entrance to a harbor is 
sometimes an advantage, 
since it breaks the force 
of incoming waves. Spits 

which form harbors have determined the location of numerous vil- 
lages and cities. The harbor of Plymouth, Mass., for example, is 
protected by a spit which makes a natural breakwater (Fig. 393). 
Provincetown, Mass., and Erie, Penn. (Fig. 395), have harbors made 
by curved spits. 

Harbors. Harbors vary greatly in value. A good harbor must, 
first of all, afford shelter from stormy seas, must be deep enough 
for large vessels, must be connected with the open ocean by a deep 
channel, and must provide room for the anchorage of many ships. 
The direction whence the storm waves come and the direction which 
the harbor entrance faces have much to do with its safety. A harbor 




Fig- 393- Map of harbor formed by spits; 
Plymouth, Mass. Broken lines indicate ap- 
proximate limits of channel. (U. S. Coast and 
Geod. Surv., Chart No. no.) 



526 



ELEMENTS OF GEOGRAPHY 



with a wide, unprotected entrance, facing the south, may be a 
good haven on a coast where the storm waves come from the east 
or northeast. The harbor of Gloucester (Mass.) illustrates this 




Fig. 394. A barrier beach with marshy tract (filled lagoon) behind it. La- 
sells Island, Penobscot Bay, Me. 

condition. The straighter and wider the channel leading into the 
harbor, the better, for long vessels cannot navigate safely a narrow, 
winding channel. This fact alone made it necessary to open a new 

entrance (Ambrose chan- 
nel) to New York harbor. 
The water near the shore 
should be deep enough to 
permit vessels to reach the 
docks, and the shore should 
be suitable for landings and 
port facilities. There also 
should be freedom from ice. 
A harbor may possess all 
these qualifications and yet 
be of little value commer- 
cially. Thus Casco Bay, 
Maine, is said to be one of 
the finest havens in the 
world, but Portland is one 
of the lesser Atlantic ports. 
For commercial importance 
(Figs. 396 and 397), a har- 
bor must have convenient interna* routes either to a large produc- 
ing region, or to one which requires many wares from the outside 
world. Thus New York has surpassed all other Atlantic ports, not 




Fig- 395- Map of harbor formed by 
curved spit; Erie, Penn. Dotted areas are 
lines of sand dunes. (Erie, Penn., Sheet, U. S. 
Geol. Surv.) 



COAST-LINES AND HARBORS 



527 




Fig. 396. Diagram showing movement of exports from the United States by 
coasts and leading ports, 19 10. Values are expressed in millions of dollars. Per- 
centages refer to proportion of total trade. 




Fig. 397- Diagram showing movement of imports into the United States by 
coasts and leading ports, 1910. Values are expressed in millions of dollars. Per- 
centages refer to proportion of total trade. 



528 



ELEMENTS OF GEOGRAPHY 



because of superior harbor facilities, but largely because of its better 
connections with the interior, where many articles of commerce are 
produced and consumed. 

Harbors at the mouths of large rivers are likely to have 
easy communication with the interior through river navigation, 
and the valleys are natural routes for railways. Thus important 
ports, like New Orleans (Figs. 396 and 397), Para, Calcutta, and 
Rangoon, are near the mouths of rivers which serve as highways 
of trade. 

Such river-mouth harbors, however, have many disadvantages. 
The current is a handicap for sailing vessels, which are still important 



cean 




Fig. 398. Map of a river-mouth harbor; Savannah, Ga. Broken lines repre- 
sent the approximate course of the channel; solid lines in the river indicate jetties 
to control currents. (U. S. Coast and Geod. Surv., Chart No. 156.) 



in coastwise commerce. Most large rivers, like the Mississippi, Ama- 
zon, and Ganges, have built large deltas, on which the stream breaks 
up into distributaries. These mouths may be blocked by deposits of 
silt and mud. Shallow water is common near the entrances, and 
this disadvantage increases as larger vessels are built. Not infre- 
quently the main discharge of the stream shifts from one mouth to 
another. In many rivers winding channels are kept open only by 
building jetties (Fig. 398). 

For these reasons expensive operations have been undertaken 
in some cases, such as the building of the Eads jetties at the South- 
west Pass from the Mississippi, in order to keep one mouth open 
and deep at all times. In other cases, the port developing in 
connection with a river has been located at the nearest favorable 
place, free from the disadvantages of the river mouth. Thus Mar- 
seilles is about 30 miles from the mouth of the Rhone, and Kurachi 



Y 

COAST-LINES AND HARBORS 529 

is some 1 5 miles from the mouth of the Indus. In each case, connec- 
tion with the river, inland, is made by rail. 

At Para, Brazil, great engineering works are necessary to facili- 
tate and cheapen the handling of the heavy traffic of the Amazon 
Basin. Para, 65 miles from the ocean, is located near the only good 
entrance to the Amazon, but in this broad mouth the water for a 
mile or two from shore is too shallow for large ocean steamships. 
To lighter most of the cargoes, valued at more than $50,000,000 
annually, meant much added labor and expense in handling. This 
handicap is to be overcome by building a long quay out in the stream, 
and filling in between the quay and the shore with the material 
dredged out of the basin in front of the quay. In this way, a depth 
of over 30 feet at the quay wall will be obtained. 

Along recently elevated coasts, the mouths of large rivers com- 
monly offer the only natural havens. River-mouth ports are also 
more common in tropical countries than elsewhere, because the 
people of these regions depend largely on waterways for internal 
communication (pp. 165, 512). 

Most of the important harbors of the world have been produced 
by the submergence of river valleys. The harbors of New York, 
Philadelphia, San Francisco, Seattle, Buenos Aires, London, Ham- 
burg, Shanghai, and hundreds of others belong to this class. The 
embayed river has many advantages over such a river as the Amazon, 
as the place for a commercial center. The entrance rarely shifts, is 
likely to be deep, and not infrequently tidal currents prevent its 
being filled by sediment. In many cases, also, the borders of the 
land are less likely to be low and swampy, and therefore are better 
suited for the development of a port. Water navigation may also be 
possible for some distance inland. Thus river craft can go from 
Shanghai far into the interior of China, and Hamburg benefits from 
a water route which reaches the Austrian frontier. 

Many harbors on embayed coasts are affected by the deposition 
of sediment in or across their entrances (Fig. 399). The direction 
in which the entrance opens, with respect to the movement of shore 
currents, is an important factor affecting the value of the harbor. 
Thus the embayed mouth of the Housatonic River receives the 
material drifted westward by the shore currents of Long Island 
Sound. As a result its entrance is very shallow, and the river mouth 
is not the site of an important port. New Haven harbor, on the 
other hand, is so situated that the shore current is turned away 



53° 



ELEMENTS OF GEOGRAPHY 






from the entrance toward deeper water. Its entrance has a depth 
sufficient for the passage of good-sized vessels, and partly for this 

reason New Haven early became an 
important shipping center. These ex- 
amples show that the relation of a har- 
bor to shore currents may be such as 
to counteract the advantages of favor- 
able communication with the interior. 
On some coasts where harbors occur 
only at rather long intervals, jetties have 
been constructed to overcome the action 
of shore currents (Fig. 400). Galveston 
harbor has been improved in this way. 

Fiords are numerous along some 
coasts, but they are relatively unim- 
portant as sites for large ports. This 
is due partly to the location of many 
fiords in high latitudes where large com- 
mercial activities are less common, and 
partly to the character of the fiords 
themselves. Many are too deep for 
anchorage in the main channel, their 
land borders are too precipitous for the 
growth of a large port, and they are 
associated in many cases with the flanks 
of mountains which hamper communi- 
cation with the interior (Fig. 281). 

The quiet upper waters of long 
fiords, however, afford good protection 
from storm waves, and every primitive 
people occupying a fiord coast early 
developed the sea-going habit. The 
configuration of certain fiord coasts may 
be taken advantage of in the future to 
develop power from the tides (Fig. 281). 

Lagoon harbors may be produced by 

the formation of barriers, or by the 

growth of coral reefs. The former are numerous along the Atlantic 

and Gulf coastal plains, but, except where combined with depressed 

coast-lines, few attain commercial value. Lagoon harbors formed 




Fig. 399. Map of river 
mouth with shallow water over 
the bar at the entrance; Cal- 
casieu Pass, La. Dotted lines 
indicate 6 foot depth. Broken 
line indicates 12 foot depth. 
Figures give depth in feet. The 
channel across the bar changes 
with every gale, so that stran- 
gers are warned not to enter 
without a pilot. (U. S. Coast 
andGeod. Surv., Chart No. 202.) 



COAST-LINES AND HARBORS 



53i 



NANTUCKET 
SOUND 



by barriers have many disadvantages. The water off shore is 
rarely deep, the inlets are commonly narrow and shallow, and many 
have such strong tidal currents as to prevent the ready passage of 
small craft. The inlets also may be closed by sediments deposited 
by waves and currents, 
unless protected by artifi- 
cial works. The lagoon, 
even if deep originally, or 
dredged to satisfactory 
depths, tends to become 
shallower through the de- 
position of (1) river sedi- 
ments, (2) material blown 
or washed from the bar, 
and (3) by the growth of 
vegetation in it. 

Most lands bordering 
lagoons are low and marshy 
on the mainland side, with 
only a low, sandy island, 
exposed to winds and 
waves, on the ocean side. 
Neither is well fitted to be 
the site of a great port. 
Galveston is the best ex- 
ample of a port with a 
lagoon harbor; large sums 
have been spent to develop 
and maintain both the har- 
bor and the city. 

Lagoon harbors due to 
coral reefs or atolls are 

fairly numerous in tropical waters, especially in the South Pacific. 
Such harbors are of little commercial importance, because most of 
them are associated with small islands, which have few people, and 
produce little. The Great Barrier Reef of Australia is a handicap 
rather than a benefit to the commerce of that country. 

The chief disadvantages of spit harbors (Figs. 393 and 395) 
result from the continued growth of the spit, the frequent movement 
of sediment into the entrance of the harbor, and the absence of a 




Fig. 400. Map of harbor maintained by 
jetties; Nantucket, Mass. Broken lines indi- 
cate approximate course of channel. (U. S. 
Coast and Geod. Surv., Chart No. in.) 



532 ELEMENTS OF GEOGRAPHY 

definite, deep channel leading toward the shore where wharfage may 
be built. Thus Provincetown harbor gradually is growing more 
shallow, and the harbor at Erie (Fig. 395) is kept open only by two 
jetties which modify the courses of the currents. 

Few harbors are suited naturally to all the demands of present- 
day commerce. Tortuous channels must be straightened, and narrow 
and shallow channels must be dredged. The Ambrose channel in 
New York harbor has been opened recently. This new entrance to 
the leading Atlantic port of the United States involved the improve- 
ment of an old channel which had a depth of only 16 feet at low tide. 
This depth was sufficient only for light-draft vessels, like scows 
and towboats. The need for a better entrance led to the deepening 
and widening of the channel so that it now has 40 feet of water at 
low tide, and a width of 2,000 feet for a length of seven miles. The 
work was done by powerful dredges at a cost of about six million 
dollars. When the channel was opened, nearly all large vessels used 
it. In a single year more than 600 trips were made by vessels of 
such size that, before the opening of the Ambrose channel, they could 
have entered only by lightering part of their cargoes, or by waiting 
for very high tide. The channel from Philadelphia to the sea must 
be dredged to a depth of 35 feet in order to accommodate the 
largest ocean vessels. A plan is on foot to make a new port at the 
eastern end of Long Island, to accommodate steamers having such 
a length that docking facilities are no longer convenient in the 
limited space along the New York water front. 

In many places the demands of commerce from lands bordered 
by regular coasts compel the expenditure of large sums for artificial 
harbors. Dover, England, has one of the greatest artificial ports 
in the world. There a series of concrete breakwaters more than two 
miles long enclose a harbor of nearly one square mile, with a minimum 
depth of 40 feet. The harbor cost more than $20,000,000. Its 
chief value is as a base for naval vessels at a strategic point on 
the English coast. A breakwater nearly two miles long has been 
constructed at Hilo, Hawaii, to protect shipping from the northeast 
trades. Similar extensive additions have been made recently to 
the works at Madras, to make that port equal to the other commer- 
cial centers of India. 

Many ports once important have declined because of the chang- 
ing conditions of commerce. To keep pace with the ever-increasing 
demands, large appropriations are made annually by our federal 



COAST-LINES AND HARBORS 533 

government. From the standpoint of commerce, harbor improve- 
ment is one of the most important phases of government work. One 
of the first harbor appropriations in our country was $30,000 to erect 
public docks at Philadelphia. But regular appropriations for river 
and harbor improvements were not made by the federal government 
until about 1826, and not over $15,000,000 was so expended prior 
to i860. Since that time, the amounts have been much larger. 

Some ports have varied in importance as a result of changes 
in the routes of world commerce. Thus the discovery of the all- 
sea route to India in 1497 shifted the main scene of commerce from 
the Mediterranean to the Atlantic coast of Europe. Mediterranean 
ports, like Venice, declined to such an extent that they almost 
ceased to be factors in the handling of European commerce. The 
opening of the Suez Canal (1869), however, made the Mediterranean 
the shortest route for trade between western Europe and the Orient; 
it led to a great expansion in the volume of commerce between those 
regions, and gave a new stimulus to Mediterranean ports. 

A similar condition is found in the Caribbean Sea and the Gulf 
of Mexico. These bodies of water bear to the Atlantic and the Amer- 
icas a relation resembling that borne by the Mediterranean to the 
same ocean and the continents of the Old World. Here also a narrow 
isthmus blocks communication with the Pacific. The Panama 
Canal, however, will open this route. By shortening the distance 
from our Atlantic ports to most Pacific points, it will make the Carib- 
bean a more important highway, and lead to expansion in trade 
between the two oceans. The neighboring ports, like those along 
the Gulf coast of the United States, will be stimulated by new traf- 
fic destined for Pacific points; they are also likely to benefit much, 
as handling centers, on account of their position as way-stations 
between the populous countries of the East and of the West. Many 
Pacific ports will be benefited similarly by freer communication 
with the Atlantic. 

Questions 

1. How is the importance of frontage on the ocean shown in the arrangement 
of countries? (Consult a political map of the world.) 

2. Why is Holland better situated than Belgium for carrying on sea trade? 

3. Why are the natives of the Malay archipelago expert boatmen? Why 
were the Incas of Peru not a seafaring people? 

4. Why is the location of Montreal better than a place at the entrance to the 
Gulf of St. Lawrence for the development of a seaport? 



534 ELEMENTS OF GEOGRAPHY 

5. What dangers threaten vessels plying along submerged coasts? Along 
recently elevated coasts? 

6. How would a submergence of 500 feet affect the Mississippi River system? 

7. What effect would an elevation of 200 feet have on Chesapeake Bay? 

8. How can the direction of shore currents be determined from the outline 
of the coast? Explain in the case of Cape Hatteras and Cape Cod. 

9. Why are there few important commercial centers on the coast between 
Cape Henry and Cape Florida? 

10. What prevents Portland, Me., from being a leading commercial center? 

11. Classify the leading seaports of the United States according to the kinds 
of harbors which they possess. 

12. Why are some harbors in tropical regions, as Manila harbor, well pro- 
tected at one season and not at another? 

13. Which Gulf ports are likely to benefit most from the opening of the 
Panama Canal? Why? 

14. What would be the probable effect on the ports of the Atlantic coast if the 
Appalachian Mountains were as high as the Sierra Nevadas? 

15. Along what kinds of coasts are the dangers to shipping greatest? Why? 

16. Along what kinds of coasts is the work of the Life Saving Service most 
difficult? Why? 

17. Why would fishing villages be more likely to develop along the coast 
shown in Fig. 381, than along that shown in Fig. 380? 

18. Which coast referred to in the preceding question is the more dangerous 
to navigation? Why? 

19. Suggest the probable course of shore currents along the coasts shown in 
Figs. 39s and 400. Which harbor is likely to be affected the more seriously by 
shore currents? Why? 

20. Suggest reasons for the movement of exports and imports by coasts and 
ports, as shown in Figs. 396 and 397. 

21. Suggest reasons why New York is a great exporting and importing city, 
and why Galveston exports much but imports little. 



References 

Brown, B. A.: Geographical Development of Seaports in the United Stales, 
in Jour, of Geog., Vol. IV, pp. 337-347. 

Chisholm: Geography and Commerce, in Scot. Geog. Mag., Vol. XXIII, pp. 
505-S22. 

Harvey: The Panama Canal and the Mississippi Valley, in World's Work, 
Vol. VII, pp. 4425-4429. 

Matthes: The Dikes of Holland, in Nat. Geog. Mag., Vol. XII, pp. 219-234. 

Reid: Coast Erosion, in Geog. Jour., Vol. XXVIII, pp. 487-495. 

Russell: North America, Ch. I. (New York, 1904.) 

Semple: Coast Peoples, in Geog. Jour., Vol. XXXI, pp. 72-89, 170-186. 

Shaler: Sea and Land. (New York, 1894.) 

Wheeler: The Sea Coast, Chs. II, III, IV, V. (New York, 1903.) 



CHAPTER XX 

DISTRIBUTION AND DEVELOPMENT OF THE LEADING IN. 
DUSTRIES OF THE UNITED STATES 



Agriculture 

Importance of agriculture. Agriculture is the most funda- 
mental industry of the United States; it furnishes, directly or 
indirectly, most of what we eat and wear, and other needs are less 
important than food and clothing. More than % of the wage-earners 
of the country are engaged in agriculture (Fig. 401). The total value 




Fig. 401. Wage-earning population in agricultural pursuits in each state in 
1900 shown by inner black circle, and by the smaller number adjacent; wage- 
earning population in all pursuits shown by the outer ring, and by the larger 
number adjacent. Numbers = thousands of wage-earners. (After Middleton 
Smith.) 

of farm lands increased about % between 1900 and 1905, and is now 
estimated at between $25,000,000,000 and $30,000,000,000. About 
half the farm lands, or a little more than one-fifth the area of the coun- 
try, is cultivated. Fig. 402 shows the relation of improved acreage to 
total farm acreage (including woodlots, etc.) in the different states. 

535 



536 



ELEMENTS OF GEOGRAPHY 



The total value of all farm products has increased each year for 
more than a decade, and reached nearly $9,000,000,000 in 1910. 
This was more than double the figure for 1900 (Fig. 403). In 1910, 




Fig. 402. Map showing relation of improved acreage (black circles) to total 
farm acreage (outer rings) in the different states in 1900. The smaller numbers 
adjacent to the circles = millions of acres of improved land; the larger numbers = 
millions of acres of farm land. (After Middleton Smith.) 

the six crops leading in value were corn, cotton, hay, wheat, oats, 
and potatoes. The United States produces about 4 /s of the corn 



.870 L 


Billions of Dollars 

1234S9T80 
















I88O 




■ 














1890 


1 
















1900 

























Fig. 403. Diagram showing total value of farm products in the United States 
for the census years 1870-1910. 

of the world (Fig. 404), 3 /s of the cotton (Fig. 405), % of the oats 
(Fig. 406), andVs of the wheat (Fig. 407). 

The leadership of the United States in agriculture is due to (1) the 






DISTRIBUTION OF INDUSTRIES 



537 




538 



ELEMENTS OF GEOGRAPHY 




DISTRIBUTION OF INDUSTRIES 



539 




54Q 



ELEMENTS OF GEOGRAPHY 




DISTRIBUTION OF INDUSTRIES 



54i 



extent, variety, and high average fertility of its soils; (2) the favorable 
climate of most sections, with range sufficient to favor the produc- 
tion of many crops; (3) the facilities for marketing products; (4) the 
energy and ability of the farming people as a whole; and (5) the 
activity of federal and state agencies in introducing new plants, 
better seeds, and scientific methods of cultivation. 

The United States Department of Agriculture has been a great help to the 
agricultural interests of the country. Agents of the department seek in foreign 
countries for new plants, suited to the special conditions of different parts of this 





Hundreds of Millions of bushels 

2 + 6 & 10 12 14 16 18 20 22 24 26 28 30 


1M0 P 


























1860 


___« 


























isro 




■ 






















1880 
























1890 










































191 


1 





Fig. 408. Diagram showing production of corn in the United States, for the 
census years 1850-1910. 



country. The department carries on investigations in many lines, and the 
results are made public through printed reports, field agents, agricultural news- 
papers, and in other ways. There are nearly 60 Agricultural Colleges and more 
than 60 Agricultural Experiment Stations in the United States, which have done 
much to advance agriculture. In a number of states, the elements of agriculture 
are taught in the public schools. 

Leading Crops 

The general distribution of crops throughout the United States is 
controlled largely by climate (pp. 188, 190, 193, 204). Their detailed 
distribution is influenced also by soil, topography, transportation 
facilities, market conditions, and other factors. It is practicable to 
consider here only the leading crops. 

Corn. Corn is our most important crop — in total value, 
acreage, and amount grown. Fig. 408 shows the great increase 
in production since 1850. More than 300 varieties of corn are known, 
but only a comparatively few are grown in large amount. The 



542 



ELEMENTS OF GEOGRAPHY 



leading varieties thrive best where there are plentiful rains with J 
prevailingly warm, sunny weather during the growing season, 
and in rich, well-drained soils. The "corn belt" is south of the 
"wheat belt," because the staple varieties of corn require a higher 
temperature and a longer warm season. Illinois, Iowa, Nebraska, 
Missouri, Kansas, and Indiana are the leading corn-producing 
states (Fig. 409). Production is increasing rapidly in the southern ! 




UNITED "STATES 

2.564 MILLION 
BUSHE.LS 



Fig. 409. Average annual production of corn in the different states (1899-1908). 
Figures in states represent production in millions of bushels. (After Middleton 
Smith.) 

states, especially where the ravages of insects have made the growth 
of cotton uncertain. The average yield of corn per acre is about 
25 bushels (1867-1906, 25.251897-1906, 25.4). Experiments show 
that this can be doubled at least by the general adoption of better 
methods of tillage, careful selection of seed, and the use of varieties 
best suited to the places in which they are grown. 

Because of the low price of corn, compared to its bulk and weight, 
little is shipped to distant markets. Most of it is used where it is 
grown, to feed stock. Corn is used also as a breadstuff, and in the 
manufacture of whiskey (p. 580), glucose, and other products. 

Corn appears to be a native of the highlands of Mexico, whence its cultiva- 
tion spread northward and southward at an early date. The colonists found it 
cultivated more or less by many of the Indians, and in many cases they promptly 



A 



DISTRIBUTION OF INDUSTRIES 543 

began to grow it. A number of the successful English settlements of eastern 
United States probably would have failed but for this food plant. As settlement 
spread westward, corn was the staple crop of much of the frontier. It was easy to 
cultivate, and usually returned a relatively large yield. It was stored easily, 
easily prepared for food, and was nourishing both for animals and man. "The 
progress of our conquest of this continent would have been relatively slow had 
it not been for the good fortune which put this admirable food plant in the 
possession of our people." 

Wheat. In the United States, wheat is the most important 
food plant. It probably originated and was cultivated first in 
Mesopotamia, but its culture spread in prehistoric times into other 
parts of Asia, and into Europe and North Africa. Its great value 
as food, the comparative ease with which it can be transported 
(Why?), and its power to adjust itself to new conditions, favored its 
wide and rapid dispersal. As a result of long cultivation and selec- 
tion under different conditions, there are now more than 1,000 
varieties of wheat, adapted to rather diverse conditions. 

Wheats are commonly classified as spring and winter wheat, red, white, hard, 
and soft. In the northern interior states spring wheats chiefly are grown, for 
plants from seeds sown in the fall are "winter-killed"; farther south, much winter 
wheat is raised. In general, soft wheats, relatively rich in starch, are used in mak- 
ing flour, while the very hard kinds, rich in gluten, are used chiefly for the manu- 
facture of macaroni (p. 204). The last is especially true of the durum wheat grown 
in the western Great Plains (p. 276). Hard and soft varieties are commonly mixed 
in making flour. The chief white wheat district is in the Pacific coast states. 

Fig. 410 shows the average annual production (1 899-1 908) of 
wheat in the different states, and Fig. 411 shows the rapid increase 
in the total production since 1850. This increase has been due 
to (1) the demands of the increasing population, (2) the occupation 
of new areas suited to wheat culture, (3) the improvement and gen- 
eral use of farm machinery, and (4) the improved conditions for 
storing, transporting, and milling the grain. As in the case of most 
other crops, the average yield per acre of wheat in the United States 
can be increased greatly. For the ten years 1897 to 1906, inclusive, 
it was 13.8 bushels; during the same time it was 32.2 bushels in 
the United Kingdom, 28 in Germany, and 19.8 in France. During 
recent years the exportation of wheat from the United States has 
decreased, as the demands of the home market have increased. 
While the acreage devoted to wheat culture in the United States 
can be increased in the semi-arid sections, and wheat may be imported, 
the greater supply needed in the future must be obtained chiefly by 
securing larger yields in the districts where wheat is already grown. 



544 



ELEMENTS OF GEOGRAPHY 



The centers of cultivation for wheat and the other leading cereals have moved 
steadily westward (Fig. 41 2). Vermont, the Genesee Valley, and the Monongahela 
Valley were among the famous wheat-growing districts of early days, but they 
produce relatively little now. Early in the last century, Baltimore was the lead- 
ing flour-making and flour-exporting city of the country. The Susquehanna and 
Shenandoah valleys furnished most of the wheat, water power developed at the 
"fall-line" ran the mills', and flour was sent in "Baltimore clippers" to European, 
West Indian, and South American markets. In the Interior, Wisconsin affords 




UNITED STATES 

640i MILLION 
BUSHELS 



Fig. 410. Average annual production of wheat in the different states (1899- 
1908). Figures in states represent production in millions of bushels. (After 
Middleton Smith.) 



a good example of a state which formerly produced much more wheat than now. 
It has been described as having been a "one-crop state" between the 1830's and 
1870's, because it grew so much wheat. In the seventies, the difficulty of com- 
peting with the newer wheat lands farther northwest helped to bring about a great 
decline in wheat production in Wisconsin, and, in turn, the development of other 
agricultural interests. 

Other cereals. Oats thrive best in a moist and relatively cool 
climate. They do fairly well in some of the southern states, where 
the climate, though warm, is moist, but do not grow well where it 
is both warm and dry. The chief area of production is in the north- 
ern Interior (Fig. 413). A small part of the crop is used as food for 
man, chiefly in the form of oatmeal; most of it is used as feed for 
animals. 



DISTRIBUTION OF INDUSTRIES 



545 



Although barley can be grown successfully under a wider range 
of climatic conditions than either wheat or corn, its cultivation in 
the United States is confined largely to the region west of Lake 











Millions of Bushels 

IOO 200 300 400 500 600 TOO 




185 O 


















I860 


















1870 


























I88O 


















1890 


















1900 


















1910 





















Fig. 411. Diagram showing production of wheat in the United States for the 
census years 1850-1910. 



Michigan (from Wisconsin to the Dakotas), and to the Pacific Coast 
(Fig. 414). In the former region it is used chiefly for the manufac- 
ture of malt liquor (p. 580), and in the latter for feed. 

Among the minor cereals grown in the United States for their 
grains or for forage are rice (Fig. 415), rye, buckwheat, kaffir com, 
and millet. 

Hay. Hay includes various grasses and legumes which are 
"cured" as food for stock. The more important ones are timothy, 
clover, and alfalfa 
(p. 454). Some of the 
cereal grasses, like 
oats and barley, some- 
times are grown for 
hay. Hay is produced 
in every state (Fig. 
416), but the c'h'ief 
area is in the eastern 
half of the country, 
north of the 37th par- 
allel. Although alfalfa is cultivated chiefly in the western part of 
the country, it probably will become of importance in the middle 
states in the near future, because of its relatively large yields per 



O CORN 
© WHEAT 
#OATS 




Fig. 412. Map showing centers of production 
of corn, wheat, and oats (1850-1900). 



546 



ELEMENTS OF GEOGRAPHY 



M,f--- 


















i V 7 


















t • 








_J^\ 


Je 






f j * y { 


7 


!8 - 1 






















/ 8 








& 7 ^C 










/ • 




1 '*. [_ 


27 < 


^ 


if 


Z^ 5 V\ ) 


£~ -M. 




1 / . 






55^^ 


I20^^^L 






U# 


VHSS^A 


\ • 6 \ 


/ ? 


I ^ 




1* 




r — X 1 






26^ 




f i 










3» 


r 










!> '5 


1 Z _ J 




1* 

1 1 
V • 


f 2 


M* 


3. > 


\j|i|!j;:|||j|F 

UNITED STATES 
849 MILLION 

eusHeLS"- 



Fig. 413. Average annual production of oats in the different states (1899- 
1908). Figures in states represent production in millions of bushels. (After 
Middleton Smith.) 




UNITED STATES 

128,473 THOUSAND 

BUSHELS 



Fig. 414. Average annual production of barley in the different states (1899- 
1908). Figures in states represent production in thousands of bushels. (After 
Middleton Smith.) 



J 



DISTRIBUTION OF INDUSTRIES 



547 



acre, its high nutritive value, and its importance in increasing the 
amount of nitrogen in the soil (p. 47). 

Cotton. The cotton of commerce is the fiber which surrounds 
the seeds of the cotton plant. The value of the fiber and the 



1 






_ ^- r u47« 


y/ 








\ 936S 7 

• ) — I 




""vla*"^ 




1 368992 


|4IB032\ 


2191 

• 


\6036\^/ 

1 A 

1 • V 











I UNITED STATES 
832,607 THOUSAND 
POUNDS 



Fig. 415. Average annual production of rice in different states (1904-1908). 
Figures represent production in thousands of pounds. (After Middleton Smith.) 

uses to which it is put depend on its length (}4 to 2^ inches), 
strength, fineness, and color. The cotton plant requires a warm, 
moist climate, and a relatively long season free from frost. These 



>J*-\ 














A • 

/ &s 

JL # ' 

( 1 3&? 
v < • 

\I43I \ 

V • \ 


"6 \_ 

• 

/ * 

137 

• 


66a r~ 

• 

/ 407 ] 

I 1 
(1553 






* **, A 

•/ • t 

^ 59p_^ 

:7~~2O60 ■ 

, l06 s V>f' 






27 v I 

793 < 

• 

'IS _ ^~~ 


584 xf vz^_ 

1 2826^ M 






5116 


^B 340 7 




2950^^ V 


3479 \^r j^>^~V 




T ' 

I 191 ! 
1 * 1 


]498 

• 


1 171 7 , 

• / 


505 • y 










T v\ 


113 \l48 

• V • 














663 # y- l__ 




\ 1 111 

V 9 .\ \ 


■" J 












V ] UNITED STATES 














S9.I37 




\ 








THOUSAND TONS 





Fig. 416. Average annual production of hay in the different states (1899- 
igo8). Figures represent production in thousands of tons. (After Middleton 
Smith.) 



548 



ELEMENTS OF GEOGRAPHY 



are the principal factors which limit the cotton-producing area of 
the United States to the southern part, east of the Great Plains 
(Fig. 417). In some other countries, the area of cotton culture may 
be extended. 

Sea-island cotton, characterized by its long, fine fiber, thrives 
best on certain islands off the South Atlantic coast, partly because 
of the high humidity. Sea-island cotton is also grown some dis- 
tance inland in southern Georgia and northern Florida (Fig. 418). 




UNITED STATES 

10,848 THOUSAND 

BALES 



Fig. 417. Average annual production of cotton in different states (1809-1908). 
Figures represent production in thousands of bales. (After Middleton Smith.) 



In general, the largest yields of cotton are obtained on the alluvial 
soils of the valley bottoms, and on the limey soils of the coastal 
plain (p. 273). Fig. 419 shows the changes in the production of cot- 
ton since 1800. About J A of the cotton grown in the United States 
is manufactured at home (p. 577), and the rest is exported. 

The cultivation of cotton in the United States began in the colonial period, 
but increased slowly until after the invention of the cotton gin (Eli Whitney, 1792) 
in this country, and of spinning machinery in England. The former made easy 
the separation of the fiber from the seed, enabling one man to do as much as 100 
to 200 could do by hand. These things, coupled for some years with unusually 
high prices for cotton, caused a great increase in its production. The output of 
the United States increased from some 2,000,000 pounds in 1791 to 35,000,000 
pounds in 1800, and 70,000,000 pounds in 1805. The development of the cotton 
industry meant also a greatly increased demand for slaves as field hands. The 
work in the cotton fields was simple, requiring little skill and few tools. In these 
and other ways it was adapted to slave labor, and, as years passed, cotton culture 
and slavery became mutually dependent. The need of new lands to meet the 
demand for cotton was a leading factor in the settlement of part of the Gulf Plains 
(p. 492). The Gulf Plain cotton crop increased from 5,000,000 pounds in 1811, 



DISTRIBUTION OF INDUSTRIES 



549 



to 150,000,000 pounds in 1826. Cotton and slavery had become dominant factors 
in the economic, social, and political life of the southeastern states, and helped to 
separate their interests in many ways from those of the northern states. Thus, 
the New England cotton manufac- 
turer (p. 577) demanded a tariff on 
imported goods to protect him against 
foreign competition; the southern 
cotton planter, who bought many 
of his supplies abroad, was injured 
by the tariff, and of course opposed 
it. The growing sectionalism be- 
tween the North and South resulted 
in the Civil War. 

Other vegetable fibers. 

Of the several plants beside 

cotton which are grown for 

fiber, only hemp and flax are 

cultivated to any large extent 

in the United States. Indeed, 

the latter is cultivated here almost entirely for its seed, from which 

linseed oil is obtained. In Russia and elsewhere, flax is produced 

chiefly for the inner bark fiber, from which linen cloths are made. 

The fiber of hemp is used to make twine, rope, bagging, etc. 




Fig. 418. Map showing (by shading) 
areas reporting sea-island cotton in 1909. 











Millions of Dales 
1 2 3 4 S 6 7 e 9 10 11 12 


1800 


1 
























1810 


■ 
























1820 


























1830 
























1840 


^ am 


BH 






















1850 


































I860 


























1870 


























I88O 


























[£££•] 
















190O 



































Fig. 419. Diagram showing production of cotton in the United States for the 
census years 1800-1910. A bale of cotton weighs 400 to 500 pounds. 



55° 



ELEMENTS OF GEOGRAPHY 



Although both plants can be grown under rather a wide range of 
conditions, the cultivation of hemp in this country is confined largely 
to Kentucky, and that of flax chiefly to the Dakotas and Minnesota. 
Tobacco. The United States is the leading country in the 
production of tobacco. It is grown in most states east of the 97th 
meridian, but a few produce the bulk of the crop (Fig. 420). The 

quality of the product 
varies greatly with the 
conditions of soil and 
climate, and with the 
care used in selecting 
the seed, cultivating 
the plants, and cur- 
ing the leaves. Many 
grades are produced. 

Vegetables and 
fruits. The growing 
of vegetables and fruits 
for distant markets 
and for consumption 
throughout the year 
has become an impor- 
tant industry mainly 
as a result of (1) im- 
provements in trans- 
portation facilities, 
especially the perfec- 
tion of "refrigerator 
cars, and (2) the development of the canning industry (pp. 567, 576). 
It is impracticable to consider here the many fruits' and vegetables 
now grown for commercial purposes in the United States. Some have 
been mentioned (pp. 188, 453, 458). Potatoes rank first in value 
among vegetables, and apples among fruits ; the cultivation of both 
is distributed widely (Figs. 421 and 422). 

The influence of refrigerator cars on the rise of industries involving the ship- 
ment of perishable commodities has been very great. The fruit and vegetable 
industries of the South and the deciduous fruit industry of the far West owe 
their development largely to the refrigerator car. It has enabled California, though 
one of the states farthest from the chief city markets, to become the leading fruit- 
growing state (p. 454). In 1877, a few bushels of peaches packed in moss were 
sent from Georgia to New York City by express, and two years later the experi- 




UNITED STATES 

740.336TH0USAND 

POUNDS 



Fig. 420. Average annual production of tobacco 
in different states (1900-1908). Figures represent 
production in thousands of pounds. (After Mid- 
dleton Smith.) 



DISTRIBUTION OF INDUSTRIES 



55i 



Li/ < 

A • 
/ 3 - 
f • 5 

{ 6 \ 

\ # \ 


• 
/ 1 


2 

• 

1 I 

• 1 

/ 6 




_J^\ .•— 




JJ fa\ A 


2 

• 

3 

• 


-i — cm 


N 


1 # \j 






/ 1 
1 '°. 


['• 


\ 2 t 


2^__X 










•^—^-p it. 


'" \ '* 


\f r :: \ 








2 . 


1' /* 




dX^J 














\ ^UNITED STATES 

V, ) 264 MILLION 
*' BUSHELS 



Fig. 421. Average annual production of potatoes in the different states (1899- 
1908). Figures in states represent production in millions of bushels. (After 
Middleton Smith.) 




UNITED STATES 

175,398 THOUSAND 

BUSHELS 



Fig. 422. Map showing production of apples in the different states in 1899. 
Figures in states represent production in thousands of bushels. (After Middleton 
Smith.) 



552 



ELEMENTS OF GEOGRAPHY 



ment was tried of shipping them by express in refrigerator boxes. Clearly peach- 
growing in Georgia for the northern markets could not become important under 
such conditions of transportation. In 1882, however, the railroad companies 
began to furnish refrigerator cars to the peach-growers, and, as a result, the 
industry spread to many parts of the state. In many places, the refrigerator car 
helped change various fruits and vegetables from luxuries, obtainable during a 
short season only, to staple articles of food available during a long season, or 
throughout the year. For example, New York City formerly obtained cantaloups 




UNITED STATES 
17.987 THOUSAND 
MILCH COWS 



Fig. 423. Milch cows on farms and ranges, 
thousands (1899-1908). (After Middleton Smith.) 



Average annual number in 



during a few weeks only from New Jersey, Delaware, and Maryland. Now the 
season for them in New York lasts from early May to late October, and some of 
them come from the Pacific coast. 

Sugar plants. Sugar-cane is a tropical and sub-tropical plant, 
and its cultivation in the United States is confined to the Gulf States, 
Georgia, and South Carolina. Louisiana grows more than 9/10 of 
the total crop of the country. In 1910, 750,000,000 pounds of cane- 
sugar were produced in the United States. 

The sugar-beet was brought into this country some forty years 
ago from central Europe, and in recent years its cultivation has 
spread rapidly. Colorado, Michigan, California, Utah, Idaho, and 
Wisconsin lead in the production of sugar-beets, but the industry 
has some importance in a dozen other states. In the West, sugar- 
beets are grown largely on irrigated lands. The production of 



DISTRIBUTION OF INDUSTRIES 



553 



beet-sugar in the United States increased more than five-fold between 
1900 and 1908, amounting, in the latter year, to some 900,000,000 
pounds. 

Animal Products of Farm and Range 
Cattle. Cattle are raised in the United States chiefly for beef, 
dairy products, and hides. Fig. 423 shows that most of the milch 
cows are in the more densely settled eastern half of the country, and 




UNITED STATES 
42.650.TH0USAND 
CATTLE.. 



Fig. 424. Cattle other than milch cows on farms and ranges. Average 
annual number in thousands (1899-1908). (After Middleton Smith.) 



that in the eastern half, most are in the northern states. The many 
cities and villages of the North Atlantic and North Central States 
require an enormous quantity of milk, and cannot draw their daily 
supplies from great distances. Herds may be kept at a greater 
distance from market in connection with the manufacture of butter, 
cheese, and condensed milk (p. 576). 

Fig. 424 indicates the distribution of cattle other than milch cows. 
This map differs from the preceding one in the smaller numbers for 
the North Atlantic States and the greatly increased numbers in the 
Great Plains and western States. Large parts of the Great Plains 
afford the best environment for cattle in the country, and much of 
the land, furthermore, cannot be used for growing crops (p. 498). 
Extensive areas are required for grazing large herds of cattle, and 



554 



ELEMENTS OF GEOGRAPHY 



with the growth of population in the East much land so used in earlier 
years has been devoted to other purposes. The United States has 
more than x /6 of the world's cattle. 

Sheep. Sheep are raised for mutton and wool. During the 
last fifty years a great change has occurred in their distribution. 
The number in most of the middle and eastern states has decreased, 
while in the western states it has increased greatly. At the beginning 



F229o\ 


fls>e 
• 

1101 

• 


/ I 58 ' 3 

\Z64Z L 

96; 

• J 


M926 
/ • 






1 jll! 

') I 

• 


4 W 

• 7 

[-'803 1 

' • 

J207 


8 04#2^1 -%. 

203 \%\W \ 




J655 

f • I 

75V < 
• 

443 ' " 
— , • 


472 
I 

~76 




1 249 

• 


) 


821 

• 

1210 
• 




'4338 


I 86 

1 • 














1891 

• 


U70 
\ • 










* 














^99 


1 UNITED STATES 
V/ 52, 2 06 THOUSAND 
SHEEP. 





Fig. 425. 
(1899- 1 908). 



Sheep on farms and ranges. 
(After Middleton Smith.) 



Average annual number in thousands 



of the period, the West had less than Vio of the sheep of the country; 
now it has more than 2 / 3 (Fig. 425; What are the probable reasons 
for the change?). The annual wool clip of the United States is more 
than 300,000,000 pounds; nearly all of it is used in American fac- 
tories, and in addition much is imported. 

Swine. About 2 /s of the swine of the world are in the United 
States. While they are raised more or less in every state, the great 
swine region (Fig. 426) is the same as the leading corn-producing 
section (Fig. 409), for corn is the chief food for swine. Nearly half 
the corn crop is disposed of in this way. 

Horses. A comparison of Fig. 427, showing the distribution of 
horses in the United States, with Fig. 402, showing the improved 
acreage and its relation to the total farm area in the different states, 



1 



DISTRIBUTION OF INDUSTRIES 



555 



indicates that the number of horses in the different states corresponds 
roughly to the amount of land cultivated. This is less striking in 
some of the southeastern states, where many mules are used to cul- 




UNITED STATES 

48.565 THOUSAND 

SWINE. 



Fig. 426. Swine on farms and ranges. Average annual number in thousands 
(1899-1908). ' (After Middleton Smith.) 




UNITED STATES 

It, 929 THOUSAND 

HOUSES. 



Fig. 427. Horses on farms and ranges. Average annual number in thousands 
(1899-1908). (After Middleton Smith.) 



556 ELEMENTS OF GEOGRAPHY 

tivate the land, because they can stand hard work in that climate 
better than horses. 

The total value of farm animals in the United States in 1910 was 
estimated at $5,138,486,000. 

Poultry and eggs. Poultry and eggs are incidental products 
of most farms. In recent years poultry-raising has become also 
a specialized industry of importance, particularly in the leading 
corn-producing states and near some of the larger cities. The value 
of the poultry and eggs produced yearly in the United States is about 
$140,000,000 and $150,000,000, respectively. 

Forest Resources and Lumbering 

The forests of the United States have been a chief factor in the 
progress of the country. They have furnished firewood and materials 
for buildings, furniture, implements, utensils, vehicles, fences, paper, 
posts, poles, cross-ties, ships, railroad cars, bridges, sidewalks, etc. 
Our dependence on the forests for material for many things is less 
than formerly. Thus, coal is now used extensively as fuel; brick, 
stone, and cement for buildings; iron and steel for ships, freight 
cars, bridges, etc. ; wire for fences ; and cement for sidewalks. Never- 
theless, the aggregate yearly drain upon the forests has increased 
with great rapidity. The United States is the leading wood-produc- 
ing country, and it is estimated that its total annual consumption (in- 
cluding that destroyed by forest fires) may amount to 100,000,000,000 
or more board-feet. 1 The total value of the forest products in 1909, 
including firewood, fence-posts, and other miscellaneous items, is 
estimated at about $1,250,000,000 — some 19 per cent more than 
the corresponding estimate of values for the products of 1908. 

Forest regions of the United States. Forests still cover about 
% the area of the United States. Although the present extent of 
forest land is more than 3/ s the original area, the amount of mer- 
chantable saw timber remaining probably is not more than half the 
original supply. The last fact is particularly significant in view of 
the comparatively short time during which the forests of the country 
have been exploited. Fig. 428 shows the five great forest regions 
of the country. Not all the land within any of these belts was for- 
ested originally, and much has been cleared. The unshaded portions 
of the map are without trees, for the most part. 

1 A board-foot is a piece of wood one foot square and one inch thick. 



DISTRIBUTION OF INDUSTRIES 



557 



(i) The Northern Forest contains both soft and hard woods, though the former 
have been of most importance commercially. The leading kinds of trees include 
white pine, red pine, spruce, hemlock, cedar, balsam-fir, birch, cherry, and sugar 
maple. (2) The Hardwood Forest contains oak, elm, hickory, cottonwood, maple, 
basswood, chestnut, ash, etc. Not all the woods of the Hardwood Forest are 
hard; cottonwood and basswood, for example, are soft. (3) In the Southern 
Forest the yellow pine predominates greatly, but in places suited to their growth 
are cypress, oak, gum, magnolia, and other hardwoods. (4) The Rocky Mountain 




FOREST REGIONS 

OFTHE 
UNITED STATES 

Th6 Unshaded Areas areTVee'esa 
Except Along th© Streams 



Fig. 428. 
Service.) 



Map showing forest regions of the United States. (U. S. Forest 



Forest is almost entirely coniferous; leading forms are the western yellow pine, 
lodge-pole pine, Douglas fir, larch, spruce, and western red cedar. (5) The Pacific 
Forest is also coniferous, consisting chiefly of Douglas fir, western yellow pine, 
redwood, western red cedar, sugar pine, etc. Fig. 429 shows the lumber produc- 
tion for 1909, by kinds of wood. The cut of yellow pine equalled that of the four 
next most important kinds; white pine, long in the lead, ranked fourth. These 
facts reflect the rapid development of lumbering in the southern and western 
states, and its decline in the Lake states (pp. 558-559). 

Distribution of the lumbering industry. As would be ex- 
pected from the distribution of the forests, lumbering is carried 
on in every state, but, as Fig. 430 shows, the production varies 
greatly. The nineteen states which in 1909 cut more than a 
billion board-feet of lumber each, furnished together more than % 



558 



ELEMENTS OF GEOGRAPHY 



of the entire cut for the United States. Great changes in the 
distribution of the industry have occurred, for as the forests 
in one region have become depleted, new areas have been opened 

up. For many years 
the northeastern states 
led in lumbering, 
which was particularly 
important in Maine 
and New York. Since 
1850, the industry has 
declined greatly in 
that region. The for- 
ests of the Great Lakes 
region were the next 
to be exploited exten- 
sively (p. 432), furnish- 
ing in 1880 about Yi 
the lumber cut of the 
country. Michigan 
and Wisconsin became 
in turn the leading 
lumbering state; now 
they rank tenth and 
eighth, respectively 
(Fig. 430). At present, 
the southern states 
contribute most to the 
lumber output (Fig. 
430), but the industry 
is expected to reach its 
climax there within a 
few years, and already 
the Pacific states are 
large producers. In- 
deed, Washington now 
leads in the business, 
while Oregon ranks ninth and California eighteenth. The accom- 
panying table shows the changes that have occurred since 1850 in 
the percentage of the total cut furnished by the leading lumbering 
sections. 





Billions of Feet 




1234 


Yellow Pine / 
Doug. Fir. . . 















■ 














Oak 

White Pine.. 

Hemlock 

Spruce 
































Western Pine 






















7eL Poplar. . 












Red Gum . . . 












Chestnut.. . . 


■■i 










Redwood. . . . 


■^ 










Beech 












Birch 








, 




Basswood . . . 












Elm 














■ 










Hickory .... 












Ash 












Cottonwood . . 
























Tamarack . . . 


■ 










Balsam Fir . . 


■ 










Sug. Pine . . . 


■ 










Tupelo 


1 










White Fir... 


■ 










Sycamore . . . 


1 










Walnut 


1 










Cherry 


1 










Lodgep'l. Pine 


1 










All others . . . 


1 











Fig. 429. Diagram showing lumber cut for 1909, 
by kinds of wood. (U. S. Forest Service.) 



reat Lakes 


Southern 


Pacific 


States 


States 


States 


6-4% 


13-8% 


3-9% 


13-6% ' 


16. 5% 


6 


2% 


24-4% 


9-4% . 


3 


8% 


33-4% 


n.9% 


3 


5% 


36.3% 


IS- 9% 


7 


3% 


27-4% 


25-2% 


9 


6% 


20.4% 


27.9% 


13 


8% 



DISTRIBUTION OF INDUSTRIES 559 



Year States 

1850 54-5% 

i860 36.2% 

1870 36.8% 

1880 24.8% 

1890 18.4% 

1900 16.0% 

1905 14-6% 

Conservation of forest resources. About 260 cubic feet of 
wood per capita per year are consumed in the United States. This 
is greater than the per capita rate of consumption in any other 
country, about ten times that in France, and seven times that in 
Germany. Stated in another way, we are taking, on the average, 
40 cubic feet of wood per acre per year from our forests. Since the 
average growth in the forests of the United States is not at present 
greater than 12 cubic feet per acre per year, it is evident that we are 
consuming wood more than three times as fast as it is being pro- 
duced in our forests. The United States cannot in the long future 
count on foreign sources of supply for ordinary structural timber, 
for other countries probably will need all they can grow. Therefore, 
if there is to be a permanent supply of wood in this country, our 
consumption cannot continue to exceed the production of our forests. 
Clearly, every means of reducing the drain upon the forests, and 
every means of increasing their production, should be encouraged. 

Altogether apart from a supply of timber, the preservation of 
forests in many places is highly desirable (1) to reduce soil erosion 
and the resultant deposition of waste on lower lands, in stream 
channels, and in harbors (p. 267); (2) to make floods less frequent 
and less dangerous (p. 366); and (3) to help equalize the flow of 
streams important for navigation, power (p. 444), or irrigation 

(P- 455)- 

The principal ways in which the forest resources of the United States should 
be conserved may be indicated briefly. (1) Losses from fires should be reduced 
(Fig. 431). These losses are of several kinds, (a) The average annual loss of 
merchantable timber is estimated at about $50,000,000; in some years (e.g., 1910) 
it has been much greater. In addition, many lives have been lost in some forest 
fires, and villages have been consumed, (b) Great loss is involved in the damage 
to young trees and seedlings, (c) After high-class timber is burned off an area, the 
latter may be occupied by inferior kinds of timber, (d) The humus in the soil may 
be consumed, reducing or destroying the fertility of the latter, (e) Erosion may 
increase on burned-over areas, and the flow of streams may become more uneven. 



560 



ELEMENTS OF GEOGRAPHY 



Forest fires are started by sparks from locomotives, by careless campers and 
hunters, by careless clearing and brush burning, by lightning, and in other ways. 

Save those due to lightning, 
nearly all may be prevented. 
So far as its funds permit, the 
Forest Service maintains a pa- 
trol in the National Forests, 
partly with a view to detecting 
fires at their beginning, and 
fighting them while they are still 
small. Some state and private 
forests also are patrolled during 
the dry season. 

(2) Waste in logging should 
be reduced so far as practicable. 
At present it averages about 
25% in the timber holdings of 
individuals and companies, and 
something less than 10% in the 
National Forests. In connection 
with logging operations, young 
trees should be protected, and 
seed trees should be left. (3) 
The wastes in sawmills and 
wood-using industries (p. 578) 
should be reduced. (4) Refuse 
wood may be used in making 
many things now manufactured 
from good timber (p. 579). 
(5) Wherever practicable, for- 
est areas should be kept fully 
stocked with rapid-growing and 
valuable species of trees. In 
this way the production of wood 
in existing forests may be in- 
creased greatly. (6) In many 
places, cut-over or burnt-over 
areas should be re-forested. (7) 
Posts, poles, cross-ties, mine tim- 
bers, pilings, shingles, etc., may 
be treated with some preserva- 
tive substance, such as creosote 
or zinc chloride, and thus ren- 
dered less subject to decay and 
to the attack of insects. Wood 
treated in this way lasts 10 to 
18 or more years longer than 
wood not so treated, so that 
its period of use is increased in 





Billions of Feet 




12 3 4 


Wash.. 
La.... 
Miss... 
N.C. 
Ark... 
Va.... 
Tex... 
Wis... 
Ore.... 
Mich. . 
Ala.... 
Minn.. 
Penn . . 
W. Va. 






































































Ga. . .. 
Tenn. . 
Fla.... 
Cal.... 

Me.... 


























S. C... 


■M 








Ky.... 


B^HM 








N. Y... 


am 








Mo.... 










N.H.. 










Ida.... 










Ind.... 


■1 








Ohio... 










Mass.. 










Vt 










Mont. . 


■i 








Md.... 


■i 








Okla... 


■ 








Ill , 


■ 








Conn.. 


■ 








Col.... 


■ 








Iowa. . 


■ 








N. M.. 


■ 








Ariz... 


1 








N.J... 


f 








Del.... 


1 








S D... 


1 








Wyo... 


1 








R. I... 


1 








Utah.. 


1 








Kas.-v. 


1 









Fig. 430. Diagram showing lumber produc- 
tion by states in 1909. (U. S. Forest Service.) 



DISTRIBUTION OF INDUSTRIES 



56i 



many cases 2 to 4 times, and in some cases much more. The general adoption of the 
practice of treating with preservatives wood used in the above ways would not only 
lessen the drain on the forests, but also give value to much inferior timber, other- 
wise nearly worthless. (8) The enormous annual waste of forest resources caused 
by insects can be reduced greatly. (9) The wasteful methods generally followed 
in the turpentine industry (p. 569) should be abandoned. (10) For many purposes, 
other material may be substituted advantageously for wood (p. 280). (11) Stand- 
ing timber is taxed in most states each year, and this leads owners in many cases 
to cut all their timber and put it on the market as soon as possible. Before the 
principles of scientific forestry can be adopted generally, these tax laws must be 
reformed. (12) Recently much has been done to conquer the diseases of forest 
trees, and much more may be done in the future. 




Fig. 431. Effects of hurricane and fire in a heavy stand of white pine on the 
Little Fork of St. Joe River, Coeur d'Alene National Forest, Idaho. (U. S. 
Forest Service.) 



The Fishing Industries 

Nature and general distribution. Fishing on a commercial 
scale is carried on from many points on the coasts of the United 
States, and on many inland streams and lakes. The total annual 



562 ELEMENTS OF GEOGRAPHY 

value of the products of the fisheries has exceeded $60,000,000 in 
recent years, the products of the coast and ocean fisheries making 
nearly ?yi of the total. The products include not only food-fishes, 
but the commercial products derived from all other marine and 
fresh-water animals. About 2 /s of the products are furnished by 
animals other than fishes, such as clams,, mussels, oysters, lobsters, 
shrimps, sponges, whale products, and fur-seal pelts. The leading 
species of fish of commercial importance are salmon, cod, shad, 
menhaden, mackerel, squeteague (or sea trout) , haddock, herring, and 
trout. 

Most marine fishing industries are the result of (1) the existence 
of extensive shallow waters off shore, to serve as feeding and breeding 
grounds for large numbers of fish; (2) convenient harbors affording 
safe havens for fishing boats; and, where the industry is dependent 
on the sale of fresh fish, (3) nearness to large centers of population. 
With present-day facilities for transportation and refrigeration, the 
last point is less important than formerly. With all these advan- 
tages, the New England coast always has been noted for its fishing 
interests, while much of the Pacific coast, with few harbors, and with 
deep waters relatively near shore, has no important fishing fleets. 

Where poor soil, rugged surface, or rigorous climate has made farming in 
coastal regions unprofitable, the people have turned to the ocean for a living. They 
become fishermen, develop into expert sailors and navigators, and supply men for 
the great merchant fleets of the world. 

Atlantic coast fisheries. Since early colonial days, the fishing 
industries of the Atlantic coast have centered in New England 
(Fig. 432). Cod, haddock, mackerel, and herring are taken in largest 
quantities. 

Most of the early settlements along the eastern coast of New England had 
fishing fleets, and many of them depended almost entirely on the industry. For 
many years, cod was the leading export of New England. The better fish were 
taken to the Catholic countries of southern Europe, while those of poorer quality 
were sold in great quantities in the West Indies to feed the slaves. Here salted 
cod was cheaper and more wholesome than meat, and would keep much longer. 
In early days many fishing towns were scattered along the New England coast 
at points where the advantages of harbors and nearness to good fishing grounds 
were combined, and the industry was carried on chiefly from small boats near 
land. As the supply of fish near at hand became inadequate, larger vessels were 
built for operations on the distant banks, and the industry centered in a few places 
having superior advantages. Gloucester has the best harbor on Cape Ann, and 
was the first fishing port of the district to secure railroad communication with 
Boston. Accordingly, the industry developed rapidly there, while it declined at 



DISTRIBUTION OF INDUSTRIES 



S63 



less-favored neighboring towns. To-day, Gloucester and Boston are the most 
important fishing ports in the United States. 

^ The whaling industry was important in New England for many years, although 
insignificant now. It was concentrated chiefly on the southeastern coast, with 
Nantucket and New Bedford as leading centers. Several factors contributed to 
its rapid decline during the third quarter of the last century, especially (1) the 
growing scarcity of whales and (2) the fact that the discovery of petroleum in 
Pennsylvania and other states diminished greatly the demand for whale-oil. 




Fig. 432. Map showing (by broken lines) principal fishing grounds off the 
coasts of New England, Nova Scotia, and Newfoundland. (After McFarland.) 



The oyster is the most important shell-fish. It thrives best 
in relatively warm waters, and in quiet, shallow estuaries and bays, 
such as those between Long Island Sound and Chesapeake Bay. 
Some 4 /s of the oysters marketed each year in the United States come 
from this section of the coast. The industry formerly depended 
entirely on natural beds of oysters. As the natural supply declined, 
the practice grew up, in many places, of "planting" young oysters, 
and leaving them to mature. 

Pacific coast fisheries. The salmon fisheries are the most 
important ones on the Pacific coast. Cod and halibut are the other 
principal species caught. The salmon industry is centered in Alaska, 
about the shores of Puget Sound, and on the Columbia River ( Fig. 
433). Most of the fish are caught in traps and weirs during the spring 
or summer run, when they ascend the rivers to spawn. At such 



564 



ELEMENTS OF GEOGRAPHY 



times, the waters sometimes have been so congested with salmon that 
the nearby canneries (p. 568), working night and day, have found 

it difficult to handle the 
fish. In 1909, for example, 
a trap near Bellingham, 
Washington, contained in 
one catch more than 100,000 
salmon. Canned salmon is 
the largest fish export of 
the United States. 

In Alaska, the salmon fish- 
eries rank next to gold mining in 
value of output. The total value 
of their product since 1868 is said 
to be more than $130,006,000. 

The largest fur-seal herd 
in the world uses the cool, 
moist Pribilof Islands 
(Bering Sea) as a breeding 
ground, but the estimated 
number of animals in it 
was reduced from some 
5,000,000 in 1867 to about 
200,000 in 1905. In recent 
years steps have been taken 
to prevent the extermina- 
tion of the herd, and to put 
the fur-sealing industry on 
a reasonable and perma- 
nent basis. 



Mining, Quarrying, etc. 

The principal mineral 
resources of the United 
States, together with their 
uses and economic signif- 
icance, were noted in 
Chapter XIII. The mining and quarrying of these resources afford 
employment to hundreds of thousands of people, and furnish raw 




Fig. 433. Map showing (by shading) 
principal salmon waters of the Northwest. 



DISTRIBUTION OF INDUSTRIES 565 

material or fuel for many other industries. The total value of 
the mineral products of the United States in 1910 was about 
$2,003,000,000. The accompanying table shows the production of 
the leading mineral substances in that year. 

Quantity Value 

Pig Iron 27,303,567 long tons $425,115,235 

Copper 1,080,159,509 pounds 137,180,257 

Gold 4,657,018 troy ounces 96,269,100 

Lead 372,227 short tons 32,755,976 

Silver 51,137,900 troy ounces 30,854,500 

Zinc 252,479 short tons 27,267,732 

Aluminum _ 47,734,000 pounds 8,955,700 

Bituminous coal 417,111,142 short tons 469,281,719 

Pennsylvania anthracite 75,433,246 long tons 160,275,302 

Natural' gas 70,756,158 

Petroleum 209,556,048 barrels 127,896,328 

Clay products 170,115,974 

Cement 77,785,141 barrels 68,752,092 

Stone 76,520,584 

Other structural materials 40,821,793 

Gypsum 2,379,057 short tons 6,523,029 

Phosphate rock 2,654,988 long tons 10,917,000 

Salt 30,305,656 barrels 7,900,344 

Mineral waters 62,030,125 gallons 6,357,590 

Distribution of mineral industries. In general, the distribu- 
tion of mineral deposits (pp. 278-288) controls that of mining and quar- 
rying, but whether or not a given mineral deposit can be worked 
profitably depends on several things. Chief among these are (1) 
its size, (2) its quality, (3) its location, (4) the cost of working it, 
and (5) market conditions. The relative importance of these fac- 
tors varies greatly with different minerals. 

(1) In many places minerals of value occur in quantities too small 
to mine. Other things being equal, the opening and equipment of 
a modern mine might be justified by a very small deposit of a valu- 
able mineral, like gold or silver, but might not be warranted by a vastly 
larger deposit of a cheap mineral, like iron. (2) There is much low- 
grade ore and coal that cannot be mined profitably in competition with 
better material of the same kind. For example, the United States 
is estimated to have more than 75 billion long tons of low-grade 
iron ore, not available (i. e., not workable with profit) under existing 
conditions, as against less than 5 billion tons which are available. 
(3) The importance of location is greatest in the case of minerals 



566 ELEMENTS OF GEOGRAPHY 

which are abundant and cheap, and least in the case of those of 
great value. Thus iron ore which could be mined with a small 
profit if in Pennsylvania or near the shores of the Great Lakes, prob- 
ably could not be mined if in Utah. On the other hand, gold offers 
great value in small bulk, and so can be transported easily. In 
recent years, therefore, it has attracted thousands of men to remote 
sections of Alaska, where most other minerals could not be mined 
with profit. Similarly, the discovery of gold in California in 1848 
brought nearly 50,000 miners there in 1849, added a new state to 
the Union in 1850, and gave it a population of 360,000 in i860. (4) 
Relatively cheap minerals are mined only where they occur in favor- 
able positions, rather near the surface; those of greater value justify 
deeper mines and greater expense. ' In classifying the coal lands 
of the Public Domain, the United States Geological Survey has 
taken a depth of 3,000 feet as the present limit for coal mining. 
Some of the copper mines of the Lake Superior region are more than 
a mile deep. (5) The output of many mines and quarries is affected 
greatly by market conditions. This is illustrated in a general way 
by the fact that the total value of the mineral products of the country 
declined from $2,071,000,000 in 1907 to $1,595,000,000 in 1908, 
largely as a result of the business depression which began late in 
1907. 

The influence of mining on the distribution of population and 
the growth of cities is discussed elsewhere (pp. 478, 499, 590, 599). 

Manufacturing Industries 

Growth of manufacturing industries. For many years, most 
of the manufacturing done in the United States took the form of 
household industries. The clothing, utensils, and implements 
used by the great mass of the people were largely "home-made," 
as is still the case in certain backward sections (p. 471). Some 
manufacturing was done in factories even in the colonial period, 
and manufactured goods were imported from other countries, 
especially for the use of the wealthier people. By 1820 or 1825, the 
factory system was established throughout much of the country then 
settled. Since 1850, and especially since 1880, the manufacturing 
industries of the United States have grown with great and increasing 
rapidity (Fig. 434), until now it ranks first among manufacturing 
countries. The total value of manufactured products for the coun- 



DISTRIBUTION OF INDUSTRIES 



567 



try amounted, in 1905, to nearly $15,000,000,000. The industrial 
growth of the last half-century has been due to (1) the increase of 
population; (2) the improved financial condition and higher stand- 
ard of living of the people; (3) the increasing supply of raw material; 
(4) the improvement of transportation facilities; and (5) the growing 
demand abroad for American goods. 

The Location of Industries 

Many manufacturing centers specialize in a few products. Thus 

Brockton, Massachusetts, is the leading boot and shoe center; Grand 

Rapids, Michigan, is famous for its furniture; and Peoria, Illinois, 

has the largest distilleries. In some cases, as in those cited, the 





1 


Billions ot Dollars 

2 3 4 5 6 7 8 9 10 11 12 13 14 ' IS 


1850 


■■ 






























I860 
































18 TO 










































18 80 










- ' 




































1890 
































fcr»TiTii 








1905 


■■■■•■■«■-: -■:■-:■ 


1 









Fig. 434. Diagram showing total value of manufactured products in the 
United States for the census years 1850-1905. 

reasons for the development of special industries in certain places 
are clear; in others, the causes are obscure. In general, the most 
important factors influencing the location of manufacturing indus- 
tries are (1) distribution of raw material, (2) command ofpower, 
(3) accessibility of market, and (4) a supply of labor. 

Distribution of raw material. The influence of the distri- 
bution of raw materials in locating the industries which use them is 
greatest in the case of (1) perishable raw materials, and (2) raw 
materials that are too bulky and too cheap to be carried far to fac- 
tories, (1) If prepared and handled carefully, fresh fruits and 
vegetables may be sent long distances in refrigerator cars (p. 550). 
But it is impracticable to do this with the large quantities used in 
the canning, preserving, and allied industries. Hence these indus- 



568 ELEMENTS OF GEOGRAPHY 

tries are located, for the most part, near the places of production. 
Thus, canning and drying fruit and making wine are important in- 
dustries in California. Indeed, California furnishes about 9/io of the 
dried fruit and some ^3 of the wine made in the United States. In 
New Jersey and Delaware ^4 of the total canned product are toma- 
toes. Similar influences appear in the case of many animal products. 
The centering of slaughtering and meat packing in Chicago, South 
Omaha, and Kansas City is due partly to the losses which result 
from shipping live animals long distances. Butter, cheese, and con- 
densed milk are manufactured extensively where large quantities of 
milk are produced, as in New York, Wisconsin, and Iowa. 

The salmon-canning industry of the Pacific coast affords a striking illustration 
of the fact that the source of supply of a perishable raw material may control the 
location of the factories using it. The industry has moved northward as the source 
of the main supply of fish has shifted. Beginning in California in 1864, the industry 
soon spread to the Columbia River and to Puget Sound. Then the supply of 
fish began to fail, and the canning business declined in consequence, first in Califor- 
nia, next in Oregon, and finally in Washington. Now the center of the industry 
is in Alaska, where nearly yi of the salmon packed in the United States are canned. 

(2) Among the raw materials that are too bulky or too cheap 
to be carried economically to distant points are many of the products 
of the quarries, mines, and forests. Hence the industries which use 
these materials are located in most cases near the sources of supply. 
In some cases, on the other hand, special conditions make it practi- 
cable to take bulky raw material to remote manufacturing plants. 
Thus granite from Massachusetts or marble from Vermont is shipped 
profitably for monumental purposes throughout the country, because 
when cut and polished in a local yard a single piece may have a market 
value of hundreds of dollars. Again, it may be feasible to take bulky 
raw material to distant points because of exceptional facilities for 
cheap transportation, as in the case of the iron ore of the Lake Supe- 
rior region (pp. 412, 431). 

The tendency of wood-working industries to keep close to the lumbering 
districts is indicated by the distribution of saw-mills, wood-pulp mills, the turpen- 
tine industry, charcoal burning, and, less strikingly, furniture making. The wood- 
pulp industry was most important originally in western Massachusetts, and later 
in Pennsylvania, but as the supply of pulp-wood decreased, the industry became 
more important elsewhere. It is now centered in Maine, northeastern New York, 
and Wisconsin, where spruce and hemlock, the principal woods used in the industry, 
are more abundant. These sections have the additional advantages of abundant 
water power and relatively near markets for the finished products. The manufac- 
ture of furniture was carried on chiefly in the East until some twenty years ago, 



DISTRIBUTION OF INDUSTRIES 569 

with New York, Philadelphia, Cincinnati, and Boston the leading centers. Now 
Chicago stands well ahead of New York, and Grand Rapids, where I /s of the popula- 
tion is employed in furniture-making (p. 440), is a close third. This migration of 
the industry followed the shifting of the center of lumbering from the northeastern 
states to the Great Lakes region (p. 558). The recent decline of lumbering in the 
region of the Great Lakes, and its growth in the Gulf states and northwestern states 
(p. 558), have led to a rapid development of furniture-making in the latter sections. 
The manufacture of tar, pitch, and turpentine has long been an important industry 
in the South. These commodities are known in commerce as "naval stores," 
because in early days the tar and pitch were used to fill the seams of ships, so as 
to make them water-tight. They are made chiefly from the sap of the long-leaf 
pine, and this is obtained, in most cases, by frequently making needlessly large 
cuts in the lower part of the trunk. The average period during which a given tree 
furnishes sap under this method is only four years, and this has caused a 
steady migration of the center of the turpentine industry. North Carolina led 
until about 1850; then South Carolina came to the front, reaching its maximum 
production about 1880. From South Carolina the industry spread into Georgia, 
where it is just beginning to decline. Now Florida leads, and the industry is 
spreading rapidly into Alabama and Mississippi. The Forest Service has developed 
new methods of obtaining the sap from smaller cuts. The general adoption of these 
methods will increase greatly the duration of the industry in a given locality. 

Most ores, except iron, have relatively high values for small bulk, but as they 
come from the mine, they are likely to be associated with much worthless material. 
Hence the metallic matter in most cases is partly separated (i.e., is concentrated) 
from the waste, at the mine. It may also be smelted (metal extracted from the 
ore) at the mine, but since in its concentrated form it is commonly valuable enough 
to bear rather heavy freight charges, it is shipped in many cases to some big 
smelter, where large-scale operation reduces the cost. Refining the metal may 
be done in turn far from the smelter. Thus, silver ore mined in Leadville, Colorado, 
may be concentrated at or near the mine, smelted in Pueblo, refined in Jersey City, 
and manufactured into jewelry in Providence, Rhode Island. 

The source of many raw materials of high value has little if any 
influence on the location of the industries which use them. This 
is determined by other factors. 

Many illustrations might be given. The United States produces no raw silk 
for the many silk mills of New York, New Jersey, and Pennsylvania. New York 
and Philadelphia have important sugar refineries, but there are no cane-fields 
nearer to them than the Gulf coast. Lowell, Massachusetts, manufactures large 
quantities of woolen goods, although New England now raises few sheep (p. 554). 

Influence of power resources. Available power may be the 
leading factor determining the location of manufacturing plants 
which use raw material suited to economical transportation. Water 
power determined the location of many of the older manufacturing 
centers of New England (p. 440). Some of these places had small 
power resources, and depended on the local supply of raw material; 



570 ELEMENTS OF GEOGRAPHY 

such places have declined. Others have continued to grow because 
they had larger power resources and were so situated that, as transpor- 
tation facilities were improved, they could use raw materials from 
increasingly distant points, and could bring in coal to supplement 
their water power. There are said to be more than forty important 
manufacturing cities in southern New England that can trace their 
start to an early advantage in water power. Nearly all of them now 
use much more steam power than water power. 

The use of coal and steam power in manufacturing increased 
rapidly after 1850. The growth of railroads steadily increased the 
number of places which could obtain coal for manufacturing, and 
also made cheaper the movement of raw materials to places situated 
favorably with respect to supplies of coal. The advantage of large 
deposits of good coal has had much to do with the remarkable in- 
dustrial development since 1850 in the region extending from western 
Pennsylvania to Illinois. The use of other mineral fuels for indus- 
trial purposes also has located certain manufactures. Thus the dis- 
covery of natural gas in western Pennsylvania, Ohio, Indiana, and 
West Virginia attracted many industries because of the cheap and 
excellent fuel offered. In many places the supply of natural gas 
failed after a few years, and as a result many factories were aban- 
doned or moved; some of the larger ones continued to operate by 
bringing in coal. 

The discovery of natural gas in eastern Indiana in 1887 started a short-lived 
"boom" in that section. "Thus scores of industrial villages sprang up from nothing. 
At the same time sleepy rural towns multiplied population by ten and were trans- 
formed into cities with metropolitan conveniences and airs. . . . The whole 
country was lighted with flaming torches which it was not worth while to turn off 
day or night. The stock in many a farmer's barnyard enjoyed the illumination of 
a quantity of gas which would have run a small factory. . . . Half of the 
whole supply was wantonly wasted and legislation was too tardy and inefficient 
to check it. In twenty years the gas was practically exhausted. Plants and 
villages were abandoned. Houses were torn down for fuel or dismembered and 
transported to be set up again in another place. . . . Many plants were 
removed across the state to the coal fields, and in the case of those that did not 
go to the coal, the coal went to them." (Dryer: Jour, of Gcog., Vol. IX, p. 21.) 

California is beginning to feel the benefit of the large supplies 
of cheap oil discovered there within the last few years. Formerly, 
the industrial development of the state was retarded by the fact 
that much fuel had to be imported from foreign countries at rela- 
tively heavy expense. 



DISTRIBUTION OF INDUSTRIES 571 

As the supply of mineral fuels diminishes, hydro-electric power 
will be used more and more in manufacturing (p. 442). But the 
ease of transmitting the power to considerable distances removes 
the need of locating the factory near the source of the water power 
(p. 441). 

. Influence of nearness to market. The advantages of a nearby 
market, or of superior facilities for shipping goods to more distant 
markets, have been leading factors in determining the location of 
many industries. 

An interesting example is afforded by the location of the leading refineries 
handling imported cane-sugar. Sugar is refined and molasses is manufactured to 
some extent in Louisiana, where cane is grown. But much cane-sugar is imported, 
and the largest refineries are in New York and Philadelphia (p. 569), in part 
because of the heavy local consumption and the excellent means of distribution 
to outside markets. Furthermore, by having the refineries at tidewater the cost 
of transporting the raw material is reduced. 

A more striking case is that of the manufacture of agricultural implements. 
The chief market for these things is in the leading farming sections. Many im- 
plements are very heavy and occupy much car-space, so that freight rates on them 
are high. For their manufacture, there is accordingly great advantage in a loca- 
tion near the chief market. As a result, there has been a steady westward migra- 
tion of the industry as the great grain districts have expanded in that direction 
(p. 544). In 1880, Ohio and New York were leaders in the industry; now, Illinois 
is far ahead of both combined, its output having increased threefold in thirty 
years. In 1880, the value of the output in Springfield, Ohio, was double that of 
Chicago; now the latter has an output nearly five times greater than that of 
Springfield, which has remained nearly stationary. 

Influence of supply of labor. The importance of a local sup- 
ply of labor in determining the location of manufactures varies greatly. 
It depends in part on the character of the industry, being more im- 
portant in the case of industries requiring skilled labor than in others. 
In general, it is much less important now than formerly, for it has 
become increasingly easy to bring laborers to any given point where 
other conditions are favorable. Doubtless, too, labor will be even 
more mobile in the future. 

In the past, the development of manufactures in some of the southern states 
and in California has been retarded by lack of a satisfactory supply of labor. On 
the other hand, the leadership of New York City in the ready-made clothing 
industry is due in part to the presence of abundant cheap labor. The long- 
continued supremacy of New England in the manufacture of cotton has been 
maintained of late years largely through the possession of expert workers. 

Other factors. In addition to the leading factors discussed 
above, there are various minor factors which may influence the 



■ 



572 



ELEMENTS OF GEOGRAPHY 



location of manufacturing industries. Thus the advantage of an 
early start has located certain industries in places without superior 
natural advantages. In most cases this advantage is associated 
closely with the question of labor. 

The boot and shoe industry of Brockton, Lynn, and Haverhill, Massachusetts, 
illustrates the advantage of an early start. The industry was established in these 
places at an early date, and by enlisting the services of many of the people, 
a supply of skilled labor was developed with enough impetus to give first rank to 
the localities. Most of the shoe factories of these cities are run by steam power, 
developed from Pennsylvania coal, and most of the leather they use is tanned 
in other states. Clearly, their leadership rests on an insecure basis, and the 
business is growing fast in other cities having more fundamental advantages. 





billions of Dollars 


NewYork 






Pennsylvania 






Illinois 






Massachusetts 








Ohio 









Fig. 435. Diagram showing value of manufactures by leading states (1905). 



In earlier years, industries frequently were established in partic- 
ular places because of a supply of local capital, but now such cases 
are relatively few and unimportant. Broadly speaking, capital 
is perfectly mobile, and goes wherever other conditions are favor- 
able. Climate may also be a direct factor in determining the loca- 
tion of manufacturing industries, though its influence is offset easily 
by other considerations. Thus the climate of the northern states 
is more invigorating than that of the southern states, and working- 
men are likely to render more efficient service, on the average, in 
the former than in the latter. Yet because of other advantages, 
the manufacturing industries of the South are growing rapidly. 

Combined influence of various factors. While many indus- 
tries are located largely or wholly by one or two factors, the distri- 
bution of others is the result of the combined influence of most or 
all of the things mentioned above. Many industries, too, have been 
located without regard to the geographic and economic conditions 
involved, and not a few have failed for this reason. 



DISTRIBUTION OF INDUSTRIES 



573 



Further illustrations of the leading factors which influence the 
distribution of manufacturing industries occur in the following pages, 
in connection with the discussion of the leading manufactures of 
the country. 

The leading manufacturing states and cities. New York, Penn- 
sylvania, Illinois, Massachusetts, and Ohio, in this order, are 
the five leading manufacturing states (Fig. 435), while New York 
City, Chicago, Philadelphia, St. Louis, and Boston are the five 
most important manufacturing cities (Fig. 436). In 1905, the com- 
bined value of the manufactured products of cities having (in 1900) 
a population of 8,000 or more was more than twice that of smaller 



Millions of Dollars 

400 300 eoo roo soo 900 1000 1100 1200 1300 1400 150a 




Fig. 436. Diagram showing value of manufactures by leading cities (1905). 

cities and rural districts. The more rapid growth of urban as com- 
pared with rural population has been one of the most striking and 
significant things in connection with the population changes of 
recent years (p. 593). It has been due in large part to the rapid 
growth of urban industries. The factories in the territory east of 
the Mississippi River and north of the Ohio and Potomac rivers 
employ about % of all the industrial wage-earners (not workers on 
farms) of the country, and contribute about the same proportion 
of the total value of manufactured products. (What are the general 
advantages which this section enjoys for manufacturing?) 

Leading Manufactures of the United States 
The Federal Census Bureau has divided the 339 classes of manu- 
factures that are carried on in the United States into 14 groups. 
These are shown in the accompanying table. 



574 



ELEMENTS OF GEOGRAPHY 



MANUFACTURING INDUSTRIES OF THE UNITED STATES IN 1905 
(Ranked according to value of product) 











Value of Products, 


Group 


Number of 
Establish- 
ments 


Capital Invested 


Wages Paid 


Including Custom 
Work and Re- 
pairing 


Food and kindred 










products 


45,79° 


$1,173,151,276 


$164,601,803 


$2,845,234,900 


Iron and steel and 










their products 


14,239 


2,331,498,157 


482,357,503 


2,176,739,726 


Textiles 


17,042 


1,744,169,234 


419,841,630 


2,147,441,418 


Lumber and its manu- 










factures 


32,726 


1,013,827,138 


336,058,173 


1,223,730,336 


Chemicals and allied 










products 


9,680 


1,504,728,510 


93,965,248 


1,031,965,263 


Metals and metal 










products other than 










iron and steel 


6,310 


598,340,758 


117,599,837 


922,262,456 


Paper and printing . . . 


30,787 


798,758,312 


185,547,791 


857,112,256 


Leather and its finished 










products 


4,945 


440,777,194 


116,694,140 


705,747,470 


Vehicles for land trans- 










portation 


7,285 


447,697,020 


221,860,517 


643,924,442 


Liquors and beverages . 


6,381 


659,547,620 


45,146,285 


501,266,605 


Clay, glass, and stone 










products 


io,775 


553,846,682 


148,471,903 


391,230,422 


Tobacco 


16,828 


323,983,501 


62,640,303 


331,117,681 


Shipbuilding 


1,097 


121,623,700 


29,241,087 


82,769,239 


Miscellaneous indus- 










tries 


12,377 


974,316,571 


187,514,312 


941,604,873 


United States 


216,262 


12,686,265,673 


2,611,540,532 


14,802,147,087 



Food and kindred products. The more important items in 
this group are slaughtering and meat-packing products; flour and 
grist-mill products; butter, cheese, and condensed milk; canned and 
preserved fruits, vegetables, and fish; and refined sugar (p. 571). 

The slaughtering and meat-packing industry tends to keep 
close to the great stock-raising areas (pp. 553-555), in order to avoid 
freight charges on waste material and to prevent the animals losing 
weight on the way to the slaughtering centers. Grazing naturally 
precedes farming in the order of economic development (Why?), 
and as the chief grazing area moved westward in front of the 
advancing agricultural zone, the slaughtering and packing industry 
followed. In early days, stock was driven from the pastures of the 



DISTRIBUTION OF INDUSTRIES 575 

Piedmont Plateau to be killed at Philadelphia, Baltimore, and 
Charleston. -The battle of Cowpens, in the Revolutionary War, 
was so called because fought about the pens of a Piedmont cattle 
ranch. Later, great numbers of cattle and hogs were driven to the 
seaboard from the settlements west of the Appalachians (p. 419). 
After the War of 181 2, the pork-packing industry found its chief 
center in Cincinnati, where it remained until about i860 (p. 422). 
During this period, the business was carried on also at various other 
points on the Ohio canals and the Ohio, Mississippi, Illinois, Wabash, 
and other rivers. By 1861-1862, the center of the industry had moved 
from Cincinnati to Chicago, and the business had declined in many 
of the river towns. Greater economy in manufacture was possible in 
a small number of large establishments than in a large number of small 
ones, and Chicago, as the greatest railroad center, had unrivalled 
facilities for assembling the stock. It is also on the northern 
edge of the corn belt (Fig. 409; Why important?), and within easy 
reach of the great grazing lands. Chicago still leads in the industry, 
contributing nearly ^3 of the total value of the products for the 
country, but the second and third centers are found on the Missouri 
River, at Kansas City and South Omaha, respectively. Apart from 
its westward migration and its tendency toward concentration at 
a few favored points, the most important thing in the later history 
of this industry has been the more and more nearly complete use of 
the waste products of the slaughter houses. Among the things 
made from these products are soap, candles, glue, gelatine, glycerine, 
ammonia, knife-handles, and fertilizer. The total value of the 
products of the industry in 1905 was $914,000,000. 

The value of the flour and grist mill products of the United 
States has increased rapidly with the growth in the production of 
cereals, and now amounts to more than $700,000,000 yearly. Two- 
thirds of the value of the output of these mills is in wheat flour. Other 
important products are rye and buckwheat flour, corn meal, and 
feed for animals. All branches of the industry have expanded toward 
the West, following the westward movement of the centers of pro- 
duction of the great cereal crops (Fig. 412). Flour and grist mills 
are distributed widely, for with the exception of a comparatively 
few large mills, they supply local demands only. Minnesota, New 
York, Kansas, Ohio, and Illinois are the leading flour-producing 
states, and Minneapolis is the most important city in the world in 
this industry (p. 441). 



576 ELEMENTS OF GEOGRAPHY 

The manufacture of dairy products in factories is a modern 
development. Formerly, this work was done almost entirely on 
the farms. In 1851, for example, there was only one cheese factory in 
the United States; in 1905, there were more than 3,600. New York, 
Wisconsin, Iowa, Illinois, Minnesota, and Pennsylvania are the six 
leading states in the industry (p. 568). The annual value of factory- 
made butter, cheese, and condensed milk is about $170,000,000. 

The canning and preserving of foods is a comparatively new 
industry in the United States, having little importance before 1850. 
Now, the total yearly value of canned foods, exclusive of meats, 
is about $100,000,000. The leading states in the industry are 
California, Maryland, and New York. The conditions which 
determine the distribution of the industry have been given (p. 567). 
The canning and preserving of fruits and vegetables are largely 
the outcome of climatic conditions. Many fruits and vegetables 
are naturally available during only a small part of the year, and 
can be grown only in certain places. The canning and preserving 
industry makes them available out of season, and in all parts of 
the country. 

Iron and steel and their products. This group of manufac- 
tures ranks second in value of product (p. 574). It comprises 
37 industries, the basic ones being the manufacture of iron and 
steel. Among the others are those producing structural iron 
work, rails, machinery, tools, hardware, tin plate (really sheets 
of iron coated with tin), and various small products. Although 
the iron and steel industry is carried on in some 27 states, nearly 
9 /io of the total output comes from Pennsylvania, Ohio, Illinois, and 
Alabama. 

The successful use of hard coal as fuel gave the first great impulse 
to iron production, and located the iron industry in eastern Pennsyl- 
vania, with Philadelphia the leading market. About the close of 
the Civil War, the center of the industry moved to Pittsburgh, where 
it still remains. A number of influences led to the change: (1) 
The hard coal of eastern Pennsylvania, because less abundant and 
in great demand for domestic use, cost more than the soft coal of 
the western part of the state. Furthermore, coke made from the 
latter was more efficient, ton for ton, than hard coal. (2) The 
Lake Superior ore was of high average grade, was mined easily, and 
could be brought to Lake Erie ports cheaply by lake. (3) The rapid 
development of the country west of the Appalachians helped to 



1 



DISTRIBUTION OF INDUSTRIES 577 

bring about the change. Although Pittsburgh did not become the 
center of the industry until after the Civil War, it had nail factories, 
foundries, and the like, before the beginning of the century. As 
early as 1815 or 1820 it was dubbed the "Birmingham of America" 
and the "Young Manchester," because it was already black with 
smoke from its factories. As indicated elsewhere (p. 431; Fig. 315), 
Lake Superior iron ore goes to Pennsylvania coal, rather than the 
reverse, because much more coal than ore is needed in the manu- 
facture of steel, and because the ore, in being sent to Pittsburgh, is on 
the way to its final market. Various phases of the iron industry 
are carried on less extensively at other cities on or near the Great 
Lakes, especially at Chicago and Cleveland, where ore and coal 
can be brought together cheaply, and where market conditions are 
good. 

In the South, Birmingham, Alabama, is the leading center of 
the iron and steel industry. In smelting iron ore it is mixed with 
limestone and coke, and when the mixture is heated in the furnace, 
the metal iron is released from the ore, and is drawn out into molds. 
At Birmingham, iron ore, coal, and limestone are found close together. 
This fortunate combination (with the Southern market) has made 
Birmingham an important city, and a leading factor in the industrial 
growth of the southern states. 

Textile manufactures. The industries of this group furnish 
the materials for nearly all our clothing and for many household 
articles, such as rugs and carpets, draperies, and bedding. Vegetable 
and animal fibers constitute the raw materials used by the 44 
textile industries. The principal industries of the group are based 
on cotton, wool, and silk. Various products are made also from flax, 
hemp, and jute. 

The textile mills of the United States consumed in 1905 nearly 2,000,000,000 
pounds of raw cotton, valued at more than $234,000,000. The value of the cotton 
manufactures was more than $450,000,000. Southern New England has led in 
the manufacture of cotton throughout the history of the industry in the United 
States, but now its leadership is threatened seriously by the South Atlantic states. 
The rate at which the industry is migrating to the latter section is suggested by 
the accompanying table, which shows that in recent years both the actual and 
proportional increase in employees, spindles operated, and raw cotton consumed 
has been much greater in the South Atlantic states than in New England. New 
England has the advantage of a much earlier start in the industry, and of a better 
supply of labor (p. 571); but the southern mills are very much nearer the cotton 
fields. Both sections possess abundant water power. This is a minor factor in 
New England, but a very important one in the South. 



578 



ELEMENTS OF GEOGRAPHY 



STATISTICS OF COTTON TEXTILE INDUSTRY 



Year 


Employees 


Spindles 


Raw Cotton Consumed 

(BALES) 




New England 


South Atlantic 


New England 


South Atlantic 


New England 


South Atlantic 


1880 
1900 
1905 


125,779 
162,294 
I55,98i 


16,317 

97,494 
120,110 


12,850,987 
13,911,241 


4,298,188 

7,508,749 


1,719,622 
1,558,094 


1,477,775 
1,813,659 



Woolen manufactures include worsted goods, suiting, blankets, carpets, felt 
goods, and wool hats. Much wool is imported for the mills, which consume more 
than 500,000,000 pounds annually. The leading manufacturing centers are the 
Middle Atlantic and New England states. The output of machine-made hosiery 
and knit goods (chiefly underwear) has increased rapidly during recent years. 
Philadelphia leads in the manufacture of hosiery and knit goods, with Utica, New 
York, second. 

The silk mills of the United States are dependent entirely upon foreign coun- 
tries for raw material. Mulberry trees could be grown and silkworms reared in 
this country, but the industry requires much hand labor, and the cost of the latter 
in the United States prevents the production of raw silk in competition with south- 
ern Europe, Japan, and China. The leading silk-manufacturing states are New 
Jersey, Pennsylvania, New York, and Connecticut, with Paterson, New Jersey, 
the leading city. 

Lumber and its manufactures. The logging-camp and lumber- 
mill furnish material for the 23 other branches of industry included 
in this group. The fundamental industries have been discussed 
(pp. 556-559). Among the products of the industries which use lum- 
ber are doors, blinds, sash, interior finish, boxes, matches, "wooden- 
ware," and furniture (p. 568). Great quantities of lumber are used 
also in building, and in certain industries included in other groups, 
such as ship building and the manufacture of carriages and wagons. 
Lumber products are manufactured on a commercial scale in every 
state, in marked contrast with the concentration of certain of the 
other greater industries, such as the manufacture of iron and steel 
and textiles. 

There is an enormous loss of material in the wood-working industries, mainly 
in the form of sawdust, shavings, and small blocks. It is estimated, for example, 
that in the furniture industry the loss in seasoning and factory amounts to 25 per 
cent; in making boxes, to about 20 per cent; and in the manufacture of vehicles 
and farming implements, to about 25 per cent. The total estimated loss in adapt- 
ing lumber to its final use in 1907 was 6,803,000,000 feet, board measure. While 
the loss can be reduced greatly by better methods and greater care, it can never 
be avoided entirely. In the future, however, such refuse material, together 
with that of the logging-camp (tops, stumps, butts, etc.) and lumber-mill 



DISTRIBUTION OF INDUSTRIES 579 

(slabs, edgings, trimmings, etc.), probably will be used more and more for the 
manufacture of various by-products. Among the possible by-products are tur- 
pentine, from the refuse of Southern pine; tannic acid (p. 580), from refuse chestnut 
wood; wood-pulp; and several chemical products. Various by-products are made 
now from refuse wood in some foreign countries, though little has been done along 
this line in the United States, because until recently wood has been both abundant 
and cheap. It has become clear, however, that this is a matter of great importance 
in conserving our forest resources, and the Forest Service is making an exhaustive 
study of the possibilities of using wood refuse. 

Chemicals and allied products. This group contains many 
manufactures which serve a wide variety of purposes. Among the 
products are paints and varnishes, dyestuff s, bleaching materials, medi- 
cines, druggists' preparations, baking powder, glue, soap, ink, various 
oils, explosives, and fertilizers. Naturally, such diverse commodities 
are manufactured in many different places, but more than half the 
products of the group as a whole come fr,om Pennsylvania, New York, 
New Jersey, Ohio, and Illinois. 

Metals and metal products other than iron and steel. Many 
things are made of gold, silver, copper, lead, and zinc (pp. 286-287}, 
such as jewelry, watches, clocks, silverware, brassware, and pins. 
Many of the 34 classes of industry belonging to this group are carried 
on extensively in the northeastern states, especially southern New 
England. The chief advantages enjoyed by this section in these 
industries are (1) an early start, and (2) the services of skilled 
workers, more numerous there than elsewhere during the early 
development of these industries. 

Paper and printing. Printing and publishing are the most 
important and most widely distributed industries of this group, 
which includes also the manufacture of wood-pulp, paper of all 
kinds, paper bags and boxes, etc. 

The principal centers of the wood-pulp industry have been noted (p. 441). 
The output of paper boxes has increased rapidly during recent years; largely be- 
cause of the increasing cost of wood, many commodities are now put up in paper 
boxes which formerly were packed in wooden boxes. The annual per capita value 
of the output in the printing and publishing business is more than ten times greater 
than it was in 1850. This significant change reflects in part the progress made in 
education, the reduced cost of reading matter, and the greater facilities for its 
distribution, such as rural free delivery. In 1905, the value of the products of 
printing and publishing in six states — New York, Illinois, Pennsylvania, Massa- 
chusetts, Ohio, and Missouri — amounted to 73 that for the entire country. 

Leather and its finished products. The basic industry in this 
group is tanning, while the dependent industries include the manu- 



5 8o ELEMENTS OF GEOGRAPHY 

facture of leather products of all kinds. Of the latter, the boot and 
shoe industry is most important, but large quantities of leather 
are used in making harnesses, saddles, trunks, bags, furniture, gloves, 
mittens, and belting, in binding books, and in other ways. For 
many years Massachusetts has been the leading shoe-manufacturing 
state (p. 572), but the industry is growing rapidly at various points 
in the middle states. 

In the past, the tanning industry has depended chiefly on local supplies of 
tannic acid, obtained usually from the bark of oak or hemlock, and as the supply 
of bark failed in one area, the industry developed in another. Massachusetts, 
the seat of the first tannery, reached its greatest importance in the industry in 
1880, when it furnished about J /6 of the total output for the country. Now it fur- 
nishes hardly yi. The industry culminated in New York in the seventies. Penn- 
sylvania took the lead when the production of New York declined, and still holds 
first rank. Later, the industry became important farther west, especially in 
Michigan and Wisconsin. Until recently, the industry was attended by an en- 
ormous waste of timber; trees were felled by thousands, from which only the bark 
was taken for the tanneries, the logs being left to rot in the woods. 

Vehicles for land transportation. The operations of the repair 
shops of steam railroad companies, the manufacture of carriages 
and wagons, and the manufacture of steam railroad cars are the 
most important of the n industries comprising this group. In 
recent years the output of bicycles has declined rapidly, while that 
of automobiles and motorcycles has increased enormously. 

The value of the automobiles made in 1900 was less than $5,000,000; in 1905, 
about $27,000,000. In 1905, automobiles were manufactured in 17 states, 
with Michigan, Ohio, New York, and Connecticut leading. The value of those 
made in Detroit was more than x /s of the total for the industry. The leadership of 
Detroit appears to be due to the impetus resulting from the success of the first 
factories established, rather than to superior natural advantages. Many factories 
now make a specialty of certain parts of the automobile, such as bodies, motors, 
lamps, and tires. 

Liquors and beverages. The value of these products increased 
nearly yi between 1900 and 1905, amounting to more than $440,- 
000,000 in the latter year. Illinois leads the states in making dis- 
tilled liquors, while Indiana, Ohio, and Kentucky follow in the order 
named. New York, Pennsylvania, Wisconsin, Missouri, and Illinois 
are the leading states in the production of malt liquors. California, 
New York, and Ohio lead in making wine. 

Peoria, Illinois, ranks first among American cities in the manufacture of 
distilled liquors. In 1905, the value of the Peoria products exceeded $42,000,000. 
This formed nearly 78 per cent of the total for the industry in the state, and repre- 



DISTRIBUTION OF INDUSTRIES 58! 

sented an increase in value of more than 57 per cent in five years. It formed,, 
furthermore, more than 69 per cent of the combined value of the products of all 
Peoria industries. Peoria was led to specialize to such an extent in the liquor 
industry, and attained leadership in it, largely because of (1) its central location 
in the corn belt of the state; (2) its transportation facilities, which enable it to 
collect at low freight rates the surplus grain of the surrounding area; and (3) an 
abundant supply of cheap coal from nearby mines. The importance of Peoria's 
favorable position in the Illinois corn belt is suggested by the fact that the dis- 
tilleries of the city used 5,809,170 bushels of corn during a recent year. This meant 
the yield from 464 acres of corn each week day of the year (counting 40 bushels 
to the acre). The manufactured product, owing to its relatively small bulk and 
large value, can bear the cost of transportation to distant markets. Nearness to 
the grain supply has also been an important factor in the manufacture of malt 
liquor in Milwaukee, Chicago, St. Louis, Cincinnati, and St. Paul. 

Clay, glass, and stone products. Some of the industries of 
this group have been noted sufficiently in earlier connections (pp. 
278-280, 407). Clay products are used most in the building trades, 
and their consumption is increasing rapidly. Ohio, Pennsylvania, 
New Jersey, Illinois, and New York lead in clay products. Pennsyl- 
vania, Indiana, and Ohio lead in the manufacture of glass. 

Deposits of quartz sand, the only raw material which enters into all kinds of 
glass, occur in many parts of the country, but the manufacture of glass on a large 
scale is fairly well localized because of the need of satisfactory fuel for the work. 
With good fuel, a skillful glass-maker can make fairly good glass from inferior 
material, but with poor fuel he cannot make good glass with the best materials. 
Gas is the ideal fuel in glass-making, because it is cleanest, and gives intense, 
uniform heat under perfect control. The leading states in the industry attained 
that position largely because of their supplies of natural gas. 

Tobacco products. These include cigars, cigarettes, chewing 
and smoking tobacco, and snuff. The value of the products increased 
from $31,000,000 in i860 to $331,000,000 in 1905. The manufac- 
ture of cigars is distributed widely, Pennsylvania, New York, and 
Ohio leading. More than % of the total output of cigarettes are 
made in New York and Virginia. Missouri, North Carolina, Ken- 
tucky, and Virginia lead in the production of chewing and smoking 
tobacco. 

Shipbuilding. Since 1850, the value of the products of this 
industry has increased nearly fourfold and the capital invested 
twenty-one fold. The latter fact means that, as iron and steel steam- 
ships replaced wooden sailing vessels, much more capital was required 
than when ships were built of wood only. The need of greater capital 
helped to bring about the concentration of shipbuilding in large 



582 ELEMENTS OF GEOGRAPHY 

establishments, with the result that there were only about half as 
many establishments in 1905 as in 1880. 

In 1905, the capital invested in the iron and steel branch of the industry was 
more than 4/s of the total capital invested in shipbuilding. Furthermore, the 
increase in the former between 1900 and 1905 was more than double the total 
amount invested in wooden shipbuilding in the latter year. 

New York, Pennsylvania, Virginia, New Jersey, and Massachu- 
setts are the leading shipbuilding states on the Atlantic coast; Ohio 
and Michigan lead on the Great Lakes; and California and Washing- 
ton on the Pacific coast. 

The rapid growth in recent years of the shipbuilding industry on the Great 
Lakes has been due to the demand created by the enormous increase in the com- 
merce of the lakes (pp. 427, 430). At the same time, of course, the development of 
shipbuilding has favored the continued growth of lake transportation. The ship- 
yards at West Bay City, Michigan, and West Superior, Wisconsin, are outgrowths 
of the wooden shipbuilding industry. Those at or near Buffalo, Lorain, Cleveland, 
Toledo, Detroit, and South Chicago are located conveniently with reference to 
the great steel mills. 

Miscellaneous industries. There are 65 industries of varying 
importance carried on in the United States which cannot be classed 
properly with any of the other groups. The combined value of their 
products in 1905 was more than $941,000,000. Among the indus- 
tries of the group whose products are of greater value are the manu- 
facture of agricultural implements (p. 571); ammunition; brooms 
and brushes; buttons; coke (p. 576); electrical machinery, apparatus, 
and supplies; fur goods; ice; mattresses and spring-beds; musical 
instruments; photographic materials and apparatus, and rubber and 
elastic goods. 

Questions 

1. (1) Explain the fact that the shores of Chesapeake Bay, Long Island, and 
Lake Michigan (east shore) were among the first sections to grow vegetables on 
a large scale for city markets. (2) Why was the business more important on the 
east shore of Lake Michigan than on the west shore? 

2. Formerly strawberries were grown extensively in a few places only, as in 
parts of Maryland, New York, Ohio, and western Michigan. Now they are grown 
on a large scale in Florida, Tennessee, Arkansas, Missouri, and other states. (1) 
Explain the relatively early development of the business in the first-mentioned 
states. (2) What permitted its later development in the other states? 

3. Name several crops not mentioned in the text which are cultivated widely 
in the United States, and several which are grown in a few places only. Explain 
the facts involved in each case. 



DISTRIBUTION OF INDUSTRIES 583 

4. Why was the original stand of timber in the Pacific Forest (Fig. 428) 
approximately equal in amount to that in the eastern Hardwood Forest, 
although the area'of the former was less than ^3 that of the latter? 

5. It is estimated that the forests of the United States (Fig. 428) contain about 
the following percentages of their original stand of timber: Northern Forest, 
30 per cent; Hardwood Forest, 21 per cent; Southern Forest, 50 per cent; Rocky 
Mountain Forest, 75 per cent; Pacific Forest, 79 per cent. Why the differences? 

6. What advantages have made New Jersey a great manufacturing state, 
in spite of the fact that it has small fuel and water-power resources, and produces 
relatively little of the raw material used by its factories? 

7. Why is manufacturing relatively unimportant in North Dakota and South 
Dakota? 

8. Explain the fact that in Nebraska most of the manufacturing is done in 
the eastern part of the state (more than 4/5 of it in two counties), while in Iowa 
it is distributed rather evenly throughout the state. 

9. (1) Name several industries not discussed in the text, the distribution of 
which is influenced to an important degree by nearness to raw material. (2) 
Name several influenced by nearness to market. 

10. Among the leading manufactures of Chicago are meat products, fnen's 
clothing, foundry and machine shop products, iron and steel, the products of 
printing and publishing houses, and railroad cars. What advantages has Chicago 
for carrying on each of these industries? 

n. Compare and contrast the general advantages for manufacturing of (1) 
Massachusetts and Texas, and (2) Utah and Ohio. 

12. Flour and sugar are household necessities. (1) Explain why the former 
is made in thousands of mills throughout the country, and the latter at compara- 
tively few points. (2) Will the situation with regard to sugar change in the future? 
Why? 

13. Why does West Virginia rank low (29th) as a manufacturing state, 
although it mines much coal (second coal-producing state in 19 10)? 

14. Explain the fact that Pennsylvania, Illinois, West Virginia, and Ohio have 
produced about % of all the coal mined in the United States. 



References 

Agriculture 

Bailey (Editor) : Cyclopedia of American Agriculture. 4 Vols. (New York, 
1907-1909.) 

Bureau of the Census: Twelfth Census of the United States; Vols, on 
Agriculture. 

Carleton: The Future Wheal Supply of the United Slates, in Yearbook, 
U. S. Dept. Agri., 1909, pp. 259-272. 

EArle: Southern Agriculture. (New York, 1908.) 

Harwood: The New Earth. (New York, 1906.) 

Hopkins: Soil Fertility and Permanent Agriculture. (Boston, 1910.) 

Hunt: Forage and Fiber Crops in America. (New York, 1908.) 

Hunt: The Cereals in America. (New York, 1904.) 



584 ELEMENTS OF GEOGRAPHY 

Smith: Agricultural Graphics; Bull. 78, Bureau of Statistics, U. S. Dept. Agri. 
Taylor: Agricultural Economics. (New-York, 1905.) 

Warren: Animal Wealth of the United States, in Nat. Geog. Mag., Vol. XVII, 
pp. 511-524- 

Widtsoe: Dry-Farming. (New York, 191 1.) 

Forest Resources and Lumbering . 

Bruncken: North American Forests and Forestry. (New York, 1908.) 

Cleveland: What Forestry Has Done; Circ. 140, U. S. Forest Service. 

Cleveland: The Status of Forestry in the United States; Circ. 167, U. S. 
Forest Service. 

Fernow: Economics of Forestry. (New York, 1902.) 

Gifford: Practical Forestry. (New York, 1902.) 

Kellogg: The Timber Supply of the United States; Circ. 166, U. S. Forest 
Service. 

Pinchot: A Primer of Forestry; Pt. I, Farmers' Bull. 173, U. S. Dept. Agri. 
Pt. II, Farmers' Bull. 358, U. S. Dept. Agri. 

The Fishing Industries 

Bureau of the Census: Fisheries of the United States, 1908. (Gov't Printing 
Office, 1911.) 

Goode, G. B., and Others: Fisheries and Fishery Industries of the United 
States. (Washington, 1884-1887.) 

Greely: Handbook of Alaska, Chs. XIV, XV, XVI. (New York, 1909.) 

Kellogg: Shellfish Industries. (New York, 1910.) 

McFarland: A History of the New England Fisheries. (New York, 191 1.) 

Spears: The Story of the New England Whalers. (New York, 1908.) 

Tarr: The Fishing Industry of New England, in Bull. Amer. Bureau of Geog., 
Vol. II, pp. 44-57- 

Tower: A History of the American Whale Fishery. (Philadelphia, 1907.) 

Mining and Quarrying 

Hubbard: Sundry articles on the various metals as factors in the settlement 
and development of the United States, in Scot. Geog. Mag., 1910-1911; Bull. 
Am. Geog. Soc, 1910; Bull. Geog. Soc. of Phil., 191 1. 

Kemp: Ore Deposits of the United States and Canada. (New York, 1901.) 

Meade: The Story of Gold. (New York, 1908.) 

Merrill, G. P.: Stones for Building and Decoration. (New York, 1901.) 

Ries: Economic Geology of the United States. 2d. ed. (New York, 1910.) 

Ries: Clays. (New York, 1906.) 

Shinn: The Story of the Mine. (New York, 1906.) 

Tower: The Story of Oil. (New York, 1909.) 

U. S. Geological Survey: Mineral Resources of the United Stales. (An 
annual publication.) 



DISTRIBUTION OF INDUSTRIES 585 

Manufacturing Industries 

Austin: The United States: Her Industries, in Nat. Geog. Mag., Vol. XIV, 
pp. 301-320. 

Bureau of the Census: Twelfth Census of the United Stales; Vols, on 
Manufactures. 

Bureau of the Census: Special Reports of the Census Office, 1905; Vols, 
on Manufactures. 

Bureau of the Census y Bulletins of Special Industries and Manufactures 
in various states. (Gov't Printing Office, 1905-1908.) 

Smith, J. R. : Story of Iron and Steel. (New York, 1908.) 

Tower: Some Factors Influencing the Location and Migration of Industries, 
in Bull. Geog. Soc. of Phil., Vol. IX, pp. 64-81. 



CHAPTER XXI 
DISTRIBUTION OF POPULATION; DEVELOPMENT OF CITIES 

Factors Affecting Density 

As preceding discussions have shown, the distribution and density 
of population are influenced by many factors — such as topography, 
climate, soil, natural resources, transportation facilities, and the 
occupations of the people. The influence of these factors may be 
reviewed by considering briefly the expansion and present distribu- 
tion of population in the United States. 

Fig. 437 shows the distribution of population in 1790, when the 
first census was taken. The great majority of the people, emigrants 
from Europe, were still east of the Appalachian Mountains. This 
was due largely to the difficulty of crossing the mountain barrier, 
the privations, dangers, and difficulties of life in the Interior, and the 
desirability of being near the Atlantic Ocean or some navigable river 
flowing into it, for purposes of trade. Furthermore, the lands east of 
the mountains and along the Great Appalachian Valley had been 
sufficient for the needs of the settlers until a few years before (about 
I 775)- The settled area was widest at the south, where the combined 
width of the Coastal Plain and Piedmont Plateau is greatest. 

In New England, the population was densest toward the south and south- 
east. This is explained by the more rigorous climate at the north; the rough 
uplands, infertile in many places; the fact that few of the rivers served as effective 
highways into the interior (Why?); and the dominance of sea-interests (fishing, 
shipbuilding, the carrying trade) in New England life. The influence of the 
Connecticut Valley and the Champlain lowland on the distribution of the frontier 
population is interesting. In New York, population was confined mainly to the 
vicinity of the Hudson and Mohawk valleys, which had fertile soils in many 
places, and afforded easy communication with New York City. The Adirondacks 
and Catskills were almost uninhabited. The sandy, forested coastal plain of 
southeastern New Jersey had a sparse population, while a strip of denser settle- 
ment extended across the state between Philadelphia and New York City. (Why? 
Compare with Figs. 439 and 441.) In the Carolinas the Piedmont Plateau, with 
its relatively small farms, had a denser population than parts of the Coastal Plain, 
with its big plantations. The influence of the Great Appalachian Valley is shown 

586 



DISTRIBUTION OF POPULATION 



587 




Fig. 437. Map showing distribution of population in the United States in 1790. 



5 88 



ELEMENTS OF GEOGRAPHY 



by the peninsula of settlement which extended southwest from Virginia. The 
settled area in southwestern Pennsylvania reflects, in part, the attractions of the 
Monongahela Valley and some of its tributaries. It was reached by several 
routes leading through the mountains, of which the one that followed the Potomac 
River and Wills Creek Water-Gap (p. 359) was most important. The large 
island of settlement in north-central Kentucky coincided with the famous "Blue 
Grass Region." Here were rich soils formed from limestones and limey-shales, 
numerous salt springs (p. 288), and navigable streams. The settlers of central 
Tennessee were also in a region of fertile limestone soils, and used the Cumberland 
River as a highway. The rough plateau lands of eastern Tennessee, Kentucky, 
and West Virginia had few settlers, or none at all. 

After 1790 population spread rapidly toward the west (Fig. 438), 
especially along such highways as the Ohio River and (later) the 
Great Lakes (p. 428). The population map for 1820 (Fig. 439) 




Fig. 438. Map showing the center of population in the United States at each 
census, 1790 to 1910. 



shows strikingly the influence of geographic features. The Adiron- 
dack Mountains and the less accessible portions of the Appalachian 
Mountains and the Alleghany Plateau remained uninhabited wil- 
dernesses. On the other hand, most of the fertile lowlands favorably 
situated and available for settlement had been occupied. The 
most striking characteristic of the western frontier was the control 
of settlement by the larger rivers, which were the principal highways 
of the time (pp. 419-422). Each one (the Red, Washita, Arkansas, 
Missouri, Mississippi, and others) was bordered for some distance by 
a narrow settled area, while the interstream tracts were still unoccu- 
pied. The influence of lines of approach from the East is illustrated 
by the belt of settlement extending from western New York around 
the southern shore of Lake Erie to Lake St. Clair. The presence of 
Indians accounts for some of the blank areas on the map, within 
the generally settled region, as in Georgia, Alabama, central and 
northern Mississippi, and western Tennessee. After the removal 
of the Indians, these areas were settled quickly. 



DISTRIBUTION OF POPULATION 



589 




v Fig. 439. Map showing distribution of population'in the United States in 1S20. 

vV 



59Q ELEMENTS OF GEOGRAPHY 

The unsettled condition of northwestern Ohio was due partly to the "Great 
Black Swamp." The lower part of the Mississippi delta and some of the lands 
along the Gulf coast also were unoccupied because swampy. Even now, some of 
these areas are uninhabited, while others recently have been made available for 
settlement by drainage (p. 459). For some years, settlers avoided the prairies of 
the northern Interior. They were thought infertile (p. 276); timber was impera- 
tively needed for buildings, fences, and fuel; they did not afford an adequate 
supply of running water for stock or mills; there was little protection from the 
bitter winds of winter; and the farmers did not know how to "break" and work 
the tough prairie sod. The gradual conquest of the prairies is one of the most 
interesting phases of the settlement of the region. The dense forests in the north- 
ern parts of the Lake states helped for a long time to keep agricultural settlers 
away from large areas. 

The appearance of the railroad introduced a new and powerful 
factor in the expansion of population. The first American railroad 
was built in Massachusetts in 1826. By the early 1850's, railroads 
had been constructed across the Appalachian Mountains from the 
leading seaports of the Northeast. In 1853 Chicago was connected 
by rail with New York City. The Mississippi River was reached 
shortly after, and in 1869 the first transcontinental railroad was 
completed. The extension of railroads opened up vast areas for 
settlement which had not been available before. This was partic- 
ularly true of large areas west of the Mississippi, whose settlement 
and development, in the absence of navigable waterways, had to 
await the railroad. Fig. 440 shows the present railroad web. 

By 1880, many parts of the West were settled (Fig. 441). Fertile 
soils had favored farming along the bases of some of the mountains 
and in many valleys, the discovery of important mineral deposits 
had attracted thousands of prospectors and miners to various places, 
and the grazing industry supported a sparse population over wide 
areas. 

The settlements in the Black Hills (southwestern South Dakota) were the 
result of the recent discovery there of gold. Most of the settlers in central and 
western Montana were farmers, located chiefly in the valleys of the principal 
streams. Besides the farmers, there were some miners. In Colorado there were 
agricultural settlements (1) along the east base of the Rocky Mountains, where, 
at many points, conditions were favorable for irrigation, and (2) in some of the 
mountain valleys. In addition, a large mining population had been attracted to 
the state by the discovery, a few years before, of rich and extensive deposits of 
gold, silver, and lead in the Leadville district (p. 479). In New Mexico, the Rio 
Grande, Rio Pecos, and upper Canadian valleys had drawn many settlers. In 
Utah, the agricultural settlements of the Mormons were spread along the base 
of the Wasatch Mountains, where there were fertile and irrigable soils (p. 445) . 
The principal agricultural settlements in Nevada were in the Humboldt Valley 



DISTRIBUTION OF POPULATION 



S9i 




592 



ELEMENTS OF GEOGRAPHY 




Fig. 441. Map showing distribution of population in the West in 1880. 



il 



DISTRIBUTION OF POPULATION 593 

and along the Central Pacific Railroad. The other settlements of the state 
depended chiefly on mining. In California, the commercial advantages of San 
Francisco Bay had attracted a relatively dense population, and some of the gold- 
producing districts were well settled. The great central valley and the more 
inviting valleys of the Coast Range were occupied by farmers. 

The lowlands west of the Cascade Mountains in Oregon and Washington were 
occupied for the most part, while in the drier regions east of those mountains most 
of the settlements were confined to the vicinity of the Columbia River and its 
tributaries. The remaining population of the West was scattered widely at 
military posts, mining camps, and on cattle ranches. 

The population map for 1900 (Fig. 442) will be interpreted readily 
in the light of the preceding discussion, and only its larger features 
need be noted here. The population of the eastern half of the 
country (east of the 96th meridian) was seven times as great as that 
of the western half. The relatively sparse population of the western 
half was due chiefly to prevailing aridity and the great extent of 
mountains and plateaus. Furthermore, many of the settled areas 
were occupied only recently. The relation of precipitation to popu- 
lation is suggested by the fact that only about x Ao of the people were 
in regions where precipitation is less than 20 inches. Similarly, 
the relation of altitude to population is shown by the fact that more 
than 95 per cent of the population lived at elevations of less than 
2,000 feet (p. 490). Since 1900, the population of many parts of 
the West has grown rapidly (Fig. 443) because of the development 
of irrigation, dry-farming, and mining, and the growth of commercial 
and industrial centers. The greatest densities (Fig. 442) are found 
in the northeastern quarter of the country. This region includes 
much of the glaciated area, with its highly productive soils; is 
unrivalled in its transportation facilities (Fig. 440); possesses vast 
resources in timber, in iron, coal, copper, and other useful minerals; 
and contains most of the great commercial and industrial centers 
of the country. 

Cities 

Cities have increased rapidly in the United States, both in num- 
ber and size. In 1850, 12.5 per cent of the total population of the 
country lived in the 85 cities which had 8,000 or more people each; 
by 1900 the percentage of the population living in such cities had 
increased to 32.4 and the number of such cities to 517 (Fig. 444). 
Nearly half (46 per cent) of the people of the country now live in 
villages and cities exceeding 2,500 inhabitants. The increasing 



594 



ELEMENTS OF GEOGRAPHY 



j? JIJL. < 


% 




s 


~~Z '-', . 'u 






fei 






IL 


^ 


jr^^iftr 










o 


^$J--?\ 




&4 




fe 



J Jf 



DISTRIBUTION OF POPULATION 



595 



concentration of population in cities has been due chiefly to the 
growth of urban commerce and industries (p. 573). The region of 
most pronounced urban development is east of the Missouri River, 
and north of the Ohio and Potomac rivers. Here are 35 of the 50 
cities which, in 1910, had a population greater than 100,000. 

The principal types of cities are (1) commercial cities, (2) manu- 
facturing cities, (3) mining cities, (4) political centers, and (5) health 




Fig. 443. Map classifying the states with respect to the percentage of increase 
of population, 1900 to 1910. (Bureau of the Census.) 



or pleasure resorts. Most large cities are both commercial and 
industrial centers, while some belong also in varying degree to one 
or more of the other classes. 

Commercial cities. Cities dependent chiefly on commerce 
grow up (1) where conditions favor the collection and distribution of 
commodities on a large scale, or (2) on important lines of communica- 
tion at points where the mode of transportation is changed. Such 
places are (1) seaports, (2) river ports, (3) lake ports, and (4) railroad 
centers. (1) The growth of seaport cities is influenced mainly by 
(a) their position in relation to great trade routes; (b) the size, resources, 
population, and accessibility of their tributary areas (hinterlands), 
and (c) the character of their harbors. The ideal harbor is large 



596 



ELEMENTS OF GEOGRAPHY 



enough to afford anchorage for many boats, deep enough to admit 
the largest ships, protected from storms, free from ice, connected 
with the open sea by a deep channel, and has shores of such a char- 
acter as to facilitate the construction of docks and the handling of 
freight (p. 525). Commercial cities are likely to grow up at or near the 
mouths of navigable rivers, for the latter serve as natural highways 
into the interior, and in many cases afford good harbors. When 
the lower courses of rivers are drowned, and so have deep channels, 





MILLIONS 

5 10 IJ 20 n » 35 40 45 50 35 W> 65 70 75 


1850 
































1860 
































1870 














20 9 1 


















1880 


























1890 














m 


1 1 








1900 


















1 1 1 1 1 



Fig. 444. Diagram showing the relation of rural and urban population in each 
census year, 1850 to 1900. The rural population is represented by the parts of 
the horizontal lines which are in solid black, while the urban population (in cities of 
8,000 or more people) is shown at the right, where the first number indicates the 
number of cities having 8,000 or more people and the second number shows what 
proportion their aggregate population made of the total population. 



such cities may be situated some distance up-stream, nearer the 
heart of the country. Thus Philadelphia and Baltimore, though 
more than 100 miles from the ocean, and Montreal, more than 800 
miles inland, are, in effect, seaports. 

San Francisco has an excellent harbor (Fig. 382), but trade with countries across 
the Pacific has been relatively unimportant; high mountains separate it from the 
interior, tending to restrict its hinterland and to handicap its trade by heavy 
freight rates; and to the east of these mountains stretch broad deserts with sparse 
populations. For years Boston, Philadelphia, and Baltimore, having good harbors 
and local hinterlands of importance, rivalled New York City in commercial im- 
portance. But the Hudson-Mohawk depression gave New York the best connec- 
tions with the interior, and the opening of the Erie Canal (p. 434) added the Great 
Lakes Region to its hinterland, enabling it to leave its competitors behind. 

(2) Since water transportation preceded railway transportation, 
most early inland cities are located at strategic points on navigable 
waterways, (a) At the head of river navigation goods are trans- 



DISTRIBUTION OF POPULATION 597 

f erred from water to land, or vice versa, for further distribution, 
and hence commercial towns develop. Thus Haverhill grew up at 
the head of navigation on the Merrimac, Hartford on the Connecti- 
cut, Albany on the Hudson, Augusta on the Savannah, and St. Paul 
on the Mississippi, (b) River cities are found also at the junctions 
of large rivers, for such places are focal points for trade. Here 
traffic coming up-stream is divided, a part going up each stream, 
while in many cases commodities descending the tributary streams 
are transferred to boats operating on the main river. Pittsburgh 
(p. 422), Cairo, St. Louis (p. 423), and Vicksburg are examples of 
places whose earlier growth, at least, was stimulated by their position 
near the confluence of important streams, (c) A decided change 
in the direction of a river's course means a division of traffic and a 
change in the mode of carriage (Why?). Cincinnati (p. 422), Nash- 
ville, and Kansas City are conspicuous examples of American cities 
that have benefited from their positions on great bends of rivers. 
Kalamazoo, Michigan, and South Bend, Indiana, are types of many 
smaller places situated similarly, (d) Falls or rapids may give rise 
to a commercial city, for river freight must be unloaded, carried 
around the obstruction, and either reloaded or forwarded by land. 
The falls (rapids) of the Ohio made Louisville, those of St. Mary's 
River gave rise to Sault Ste. Marie, and the growth of Buffalo was 
aided by the falls and rapids of the Niagara. 

(3) All the more important cities ranged along the Great Lakes 
started as commercial towns — as centers of exchange and trans- 
fer — and their commercial activities still dominate. As noted 
elsewhere (p. 427), their immediate location was determined in most 
cases by natural lines of communication leading from the shores of 
the lakes. It is interesting to note that the trade which contrib- 
uted chiefly to the growth of most of the Great Lakes cities has 
been in one or two classes of goods. Duluth, Marquette, Ashland, 
and several other Lake Superior ports grew up with the develop- 
ment of the iron mines and the shipment of ore to the Lower Lakes. 
Similarly, the growth of Ashtabula, Conneaut, Cleveland, and other 
Lake Erie ports was stimulated by the transfer of ore from boat 
to rail on its way to the Pittsburgh region (Fig. 315), and by the 
return trade in coal coming from the nearby Ohio and Pennsylvania 
fields. Milwaukee and Chicago are great grain and flour shipping 
points, and the latter formerly had an immense lake trade in lumber 
(pp. 433, 437)- 



598 ELEMENTS OF GEOGRAPHY 

Chicago became the greatest lake port because of its superior geographic 
advantages, (i) It is near the head of Lake Michigan, which extends farther than 
the other lakes into the heart of the country. (2) It is located more centrally than 
its rivals with reference to the richer areas of glacial soil and the areas leading in 
the production of corn (Fig. 409), wheat (Fig. 410), swine (Fig. 426), and cattle 
(Fig. 424). (3) All land traffic from the Northwest to the eastern part of the 
country must pass around Lake Michigan, and is therefore tributary to Chicago. 
The latter is accessible also by land from the south and east, from which directions 
many railroads have been built to Chicago to meet the traffic of the West and 
Northwest. Because of its strategic position, Chicago is the greatest railroad 
center in the world (Fig. 440). 

The importance of water transportation to the growth of the 
leading cities of the country is reflected in the fact that of the 28 
cities having in 1910 a population of more than 200,000, 23 are situ- 
ated on navigable waters. Of the 23, 10 are seaports, 7 are on the 
Mississippi System, and 5 are on the Great Lakes. 

(4) All the important seaports, river ports, and lake ports of 
the United States are also more or less important as railroad centers. 
There are also a number of large cities without water transporta- 
tion, like Columbus, Ohio, and Indianapolis, which now owe their 
commercial importance entirely to the fact that they are at the 
junction of several railroad lines. The greater cities of the United 
States had attained importance because of their natural advantages, 
before the appearance of railroads. Railroads were built to them 
to share in existing trade, which they later helped to increase. On 
the other hand, the extension of railroads throughout the country 
caused a multitude of small cities and villages to spring up on sites 
without natural advantages. Such places serve as collecting and 
distributing points for the surrounding country, and, if junctions, 
derive more or less benefit from the resulting exchange and trans- 
fer of traffic. 

While the more important conditions which give rise to com- 
mercial centers have been mentioned, villages and cities may grow 
up at critical points on lines of communication not included in the 
foregoing classification. Thus a ford or ferry on a river may locate 
a town. Harrisburg, Pennsylvania, developed from Harris' Ferry, 
where a land route toward the west crossed the Susquehanna River; 
Zanesville, Lancaster, and Chillicothe, Ohio, grew up where an 
important early road (Zane's Trace) crossed the Muskingum, Hock- 
ing, and Scioto rivers. Again, a mountain pass upon which impor- 
tant trade routes focus may give rise to a city. Cumberland, Mary- 



DISTRIBUTION OF POPULATION 599 

land, has grown up in front of Wills Creek Water-Gap, important 
since the colonial period (p. 359). The growth of Denver has 
been stimulated by its relation to several of the passes in the Rocky 
Mountains. 

Manufacturing cities. Most large cities which are dominantly 
commercial centers are important also as manufacturing centers 
(P- 573), for their transportation facilities favor the assembling of 
raw materials and the marketing of manufactured products, and 
abundant labor is available. New York, the commercial metropolis 
of the country, leads also in manufacturing; Chicago, the leading 
inland commercial city, is the second industrial center; and Phila- 
delphia, the fourth commercial center, is third in industry (Fig. 
436). On the other hand, all industrial cities are necessarily, in 
varying degree, trade centers. In most cities, therefore, commer- 
cial and industrial activities are blended in varying proportions 
determined largely by geographic conditions. The factors which 
control the distribution of manufacturing industries (pp. 567-572), 
obviously control also the location of the cities to which those indus- 
tries may give rise. Most distinctly industrial cities are located 
in response to (1) power resources, like many of the New England 
cities (p. 570), or (2) raw materials, like Birmingham, Alabama. 

Mining cities. Many villages and cities, especially in the 
West, have developed from rude camps about mines. As the mining 
industry in a given locality grew, tents gave place to buildings of 
wood and brick, business and professional men appeared to supply 
the needs of the miners, and busy settlements resulted, which in 
many cases became cities in a few years. Scran ton (Pennsylvania), 
Joplin (Missouri), Deadwood (South Dakota), Cripple Creek (Colo- 
rado), and Placerville (California) are types of a large number of 
cities and towns which have grown up solely because of the wealth 
of adjacent mines. Many cities of this class are in places where, 
without the mines, there probably never would have been cities 
(p. 499). 

Many cities at which there are no mines depend largely on the 
mining industry. Thus Pueblo (Colorado) and Anaconda (Mon- 
tana) were founded primarily for extracting metals from ores. Again, 
Sacramento and Denver first became important as outfitting and 
supply stations for nearby mines. Indeed, there are few cities 
in the West which have not been influenced by the mining 
industry. 



600 ELEMENTS OF GEOGRAPHY 

The ruins of scores of abandoned mining towns are scattered throughout the 
leading mining states. They were built hurriedly in boom times, and deserted 
because of the failure of the mineral deposit, the discovery of richer deposits else- 
where, or for some other reason. 

Political centers. Few cities are merely political centers, 
for even though founded as such, their growth is almost certain to 
attract commercial, if not industrial, enterprises. Washington, 
D. C, is a conspicuous exception. In locating state capitals, acces- 
sibility for the majority of the people has been a leading considera- 
tion. In states having a fairly uniform distribution of population 
and equal facilities for travel, the political center tends toward the 
geographic center. Thus the capital of Illinois shifted from Kas- 
kaskia to Vandalia, and later to Springfield; that of Tennessee from 
Knoxville to Nashville; and that of Pennsylvania from Philadelphia 
to Harrisburg. The centrally located capitals of Ohio, Indiana, 
Iowa, Missouri, and South Dakota illustrate the same principle. 
On the other hand, where the mass of the population is in one sec- 
tion of the state little attention has been paid to the question of the 
geographical center. Thus Boston, Albany, Lincoln, and Topeka, 
though far from the geographic centers of their respective states, 
are not far from the centers of population in each case. The ques- 
tion of accessibility was considered, among others, in choosing the 
site for the national capital, but with the acquisition and settlement 
of the West it has come to have a marginal location. 

Health and pleasure resorts. The leading cities of this type 
have been stimulated in their growth by geographic conditions which 
make them attractive to the tourist or beneficial to the invalid; 
most of them are ocean, mountain, or natural spring resorts. The 
attraction of the ocean resorts lies partly in their facilities for boat- 
ing and bathing, but chiefly in the occurrence of the cool sea-breeze 
(p. 114) in the hot days of summer, and in the tempering effects of 
winds from the sea in winter. Newport and Atlantic City are typical. 

Atlantic City, situated on one of the barrier reefs ("beaches") off the New 
Jersey coast, has a good beach with excellent bathing and a climate so tempered 
by the ocean that it is frequented by many visitors in winter as well as in summer. 
Fogs are rare, and malaria (so common in many parts of the state; p. 460) is almost 
unknown, owing to the extensive areas of pine forest and dry, sandy soil which lie 
inland from this part of the coast. Although the permanent population of Atlantic 
City is only 46,000, the transient summer population is more than a quarter 
of a million. 



DISTRIBUTION OF POPULATION 601 

Asheville (North Carolina) and Colorado Springs are among the 
best-known mountain resorts (pp. 212, 4S2) of the United States, 
and Hot Springs, Arkansas, is the most prominent health resort 
created by "medicinal" springs (p. 329). Los Angeles and several 
neighboring places in southern California have become important 
resorts chiefly for climatic reasons. 

Location of early cities. At one time the concentration of people 
in villages and cities was chiefly because of the necessity for defense. 
For this reason many old cities are located in places affording 
protection, as on hills and islands. Considerations of defense as 
well as of trade located many of the towns founded in this country 
during the colonial period. 

The site of Boston was chosen because of (1) its strength for defense, (2) its 
harbor, and (3) a supply of good water. Boston peninsula was connected with 
the mainland by a narrow isthmus, so low that for years it was submerged at high 
tide if a strong wind blew off the bay. This favored defense toward the land. The 
harbor is roomy, deep, farther inland than any other north of Cape Cod, and is 
located centrally on the coast of Massachusetts. This favored trade, and helped 
to make Boston from the outset the leading town of the colony. New York was 
founded on Manhattan Island for safety and in the expectation that the Hudson 
River would, as it did, give it command of the trade of a large district. Quebec 
was founded to guard the St. Lawrence highway and to com m and the fur trade of 
the Interior. The river is much narrower there than at any point farther down- 
stream (Why advantageous?) ; the inland location was expected to afford security 
from European enemies; and the "Heights of Quebec" furnished an ideal site 
for a fortress. Montreal was laid out on a hilly island in the St. Lawrence River, 
opposite the mouth of the Ottawa River. Thus it was reasonably safe from 
unexpected attack, and able to draw upon the trade of both valleys. 



Questions 

1. Discuss the leading occupations of the United States as factors affecting 
density of population. 

2. Why are there more important cities in the United States on the Atlantic 
coast than on the Pacific coast? 

3. Compare and contrast the commercial advantages of the seaports of south- 
eastern and northeastern United States. 

4. Why are there fewer cities on the Great Lakes in Canada than in the United 
States? 

5. Give examples, not mentioned in the text, of American and foreign cities 
which have profited from their position (1) on rivers at the head of navigation, 
(2) at the junctions of important rivers. 

6. Lexington was for years the largest community in Kentucky. Now the pop- 
ulation of Louisville is more than six times that of Lexington. Explain the change. 



602 ELEMENTS OF GEOGRAPHY 

7. Why has Chicago derived greater commercial advantages from its location 
near the head of Lake Michigan, than Duluth has from its position near the head 
of Lake Superior? 

8. Explain the fact that y I0 of the cities in the United States having in 1910 
a population of more than 100,000 are Situated east of the Missouri River and north 
of the Ohio. 

9. (1) Explain the relatively small population (1900) of (a) southern Florida 
and (b) northern Wisconsin and northern Michigan, as shown by Fig. 442. 

(2) Explain the distribution of population in (a) Montana, (b) the belt through 
southeastern Idaho and Utah, and (c) New Mexico. 

(3) Account for the areas of relatively dense and of relatively sparse population 
in California. 

(4) Cite illustrations (not involved in preceding questions) from the map, 
showing the influence on the distribution of population of (a) topography, (b) 
means of communication, and (c) natural resources. 

10. (1) Why is the railroad web (Fig. 440) thickest in the northeastern quarter 
of the country? 

(2) Account for the thinness of the railroad net in northern New England, 
northern New York, and the northern Lake Region. 

(3) Why is the dominant direction of railroads east-west in the Great Plains? 

(4) Why the relatively small railroad mileage of the western half of the country? 

(5) Explain the distribution of railroads in California. 

(6) Interpret the dominant north-south direction of the railroads in the southern 
Interior. 

(7) Explain the striking gap in the railroad net between the lower Missouri 
and lower Arkansas rivers. 

References 

Bureau of the Census : Statistical Atlas of the 12th Census; also Geographical 
Distribution of Population; Bull. 1, U. S. Census Office. (Washington, 1903.) 

Brigham: Capacity of the United States for Population, in Pop. Sci. Mo., 
Vol. LXXV, pp. 209-220. 

Chisholm: On the Distribution of Towns and Villages in England, in Geog. 
Jour., Vol. IX, pp. 76-87; Vol. X, pp. 511-530. 

Hubbard: The Precious Metals as a Geographic Factor in the Settlement and 
Development of Towns in the United States, in Scot. Geog. Mag., Vol. XXVI, pp. 
449-466. 

McGee: Prospective Population of the United States, in Science, N. S., Vol. 
XXXIV, pp. 428-435. 

Sears: Geographic Conditions that Make Great Commercial Centres, in Bull. 
Am. Geog. Soc, Vol. XXX, pp. 281-304. 

Semple: Some Geographic Causes Determining the Location of Cities, in Jour, 
of Sch. Geog., Vol. I, pp. 225-231. 

Tower: The Geography of American Cities, in Bull. Am. Geog. Soc, Vol. 
XXXVII, pp. 577-588. 



INDEX 



Abrasion by sand, 314 
Africa, area and population in temper- 
ate zone, 178 

area and population in tropics, 155 

general features of, 41 

rivers of, 414 

trade with U. S., 229 
Agricultural colleges, 541 
Agricultural implements, manufacture 

of, 57i 
Agriculture, 535-536 

on alluvial fans, 363 

in equatorial forests, 511 

in irrigated lands, 453, 458 

leadership of U. S. in, 536 

in oases, 504 

in mountains, 474 

and rainfall, 118, 119, 124, 188, 209 

in semi-arid regions, 495 

in tropical grass lands, 165 
Air. See Atmosphere 
Alabama, 492, 493 
Alaska, agriculture in, 193, 222 

canning industry in, 568 

climate of, 192, 219, 220 

coast of, 516 

fisheries of, 564 

glaciers of, 383, 385, 386 

precipitation in, 123 
Aleutian Islands, 302 
Alfalfa, 47, 454, 545 
Alluvial cones and fans, 361, 363 
Alluvial plains, 364 
Alluvial terraces, 376 
Alluvium, 265 
Alps Mountains, 469, 483 

glaciers of, 385 

life on sunny vs. shady slopes, 69 

stock-raising in, 477 

zones of vegetation in, 476 
Altitude and climate, 198, 211 
Altitude and pressure, 103 
Altitude and temperature, 67, 77, 210 
Aluminum, 287, 565 
Amazon River, 165, 416, 519, 528 



American waterways, 416-440 

improvement of, 438 
Andes Mountains, 468 

as climatic barrier, 122, 166, 191 
Anemometer, 118 
Animal life, and ancient ice-sheets, 409 

of Antarctic region, 219 

of Arctic region, 222 

in caverns, 331 

in deserts, 500 

in the sea, 252-255 

and soil formation, 263 

in tropical forests, 509 

See Life 
Animal products, 553 
Antarctic circle, 22 
Antarctic region, climate of, 21S 

life of, 219 
Antarctica, snow and ice of, 218, 386 
Anthracite coal, 479 
Anticyclones, 128, 129-136 
Aphelion, 13 

Appalachian Mountains, and early 
distribution of population, 586, 
588 

and early western settlements, 419 

forest reserve in, 482 

in history, 470 

inhabitants of southern, 473 

soils of, 275 

structure of, 466 
Apples, 550, 554 
Arabia, desert of, 501, 503, 504 
Arctic circle, 22 
Arctic regions, climate of, 219 

ice of, 219 

life in, 221-224, 507 
Arid climate in temperate zones, 198 
Arid regions of the U. S., 122, 123, 

200-202 
Arid plains, life in, 499-507 
Artesian wells, 326 

in oases, 503, 504 
Asia, area and population in tropics, 

155 
603 



t 



604 



INDEX 



Asia — continued 

caravan trade in, 506 

climate of, 206 

climatic changes in, 124 

general features of, 40 

monsoons of, 115-117, 1 71-173 

trade with U. S., 229 
Asiatic cholera, 173 
Asteroids, 8 

Australia, area and population in 
temperate zone, 178 

area and population in tropics, 155 

climate of, 167, 178, 493 

general features of, 41 

grazing in, 495 

Great Barrier Reef of, 255, 531 

population of, 167 
Automobiles, 580 
Atlantic City, 600 
Atlantic coast fisheries, 562 
Atmosphere, circulation of, 111-113 

composition of, 46 

density of, 44 

functions of, 44 

future of, 53 

heating of, 62 

height of, 45 

history of, 52 

impurities of, 46 

relation to rest of earth, 44 

temperature of, 55 

weight of, 44, 102 

work of, 316 
Atmospheric pressure, and altitude, 103 

and boiling, 104 

distribution of, 104 

Bacteria, of air, 51, 120 

nitrogen-fixing, 47 
Baltimore, 240, 544, 575, 596 
Barley, 69, 188, 545, 546 

climate for, 193 

distribution of, 209 
Barometers, 102, 103 
Barriers, 523 
Bars, 524, 525 
Base-level, 344 
Base-level plain, 350 
Batholiths, 309 
Beach, 523 

Birmingham, 577, 599 
Bituminous coal mined in U. S., 565 
Blizzards, 136 
Block mountains, 465 
Bogota, 156, 162 



Bolivia, climate of, 68, 174 

crops of highlands, 175, 210 

people of, 486 
Boot and shoe industry, 572, 580 
Borax deposits, 202 
Bore, tidal, 248 

Boston, 517, 563, 569, 573, 596, 600, 601 
Brazil, 78, 154 
Brick, manufacture of, 407 
British Isles, advantages of isolation, 34 

agriculture in, 193, 194 

climate of, 77, 206, 245 

fisheries of, 254 

rivers of, 415 
Bubonic plague, 173 
Buckwheat, 545 

Buffalo, 427, 429, 435, 441, 462, 582, 597 
Buffaloes, 496 

bones used for fertilizer, 271 
Building stones, 278 
Butte, 499 

Cables, 227 

Caldera, 303 

California, climate of, 186, 187, 191 

fruit of, 188, 454, 568 

gold in, 566 

oil in, 570 
California Trail, 471 
Camel, 501, 506 
Campos, 165 

Canada, agricultural conditions in 
eastern, 395 

chinook winds in western, 138 

climatic effects in eastern, 207 

fur trade in western, 484 

sunlight and crops in western, 22 

trade with U. S., 229 

vegetation of northern, 221 
Canals, 359, 433~438 

in foreign countries, 437 

influence of, 423 

in U.S., 433-437 
Canning industries, 568, 576 
Canyons, 354~355 / 

and human activities, 352 
Caravans, 501, 506 
Carbon dioxide, 46, 48-50, 282 

in sea-water, 236 
Caribbean Sea, 154, 533 
Catskill Mountains, 466, 474, 483 
Cattle, 553 
Caverns, 330 
Cayambe, 173 
Cement produced in U. S., 278, 565 



k 



INDEX 



605 



Cereal crops in high latitudes, 69 
Cereals, centers of cultivation in U. S., 
544. 

and climate, 209 

See Corn, Wheat, etc. 
Chalk deposits, 232 
Changes of level of land, 291, 394 
Chemicals and allied products, 574, 579 
Chicago, 427, 429, 433, 437, 497, 568, 
569, 57i, 573, 575, 577, 597, 598, 
599 

Sanitary and Ship Canal, 439, 462 

water supply of, 462 
Chile, climatic zones in, 194 

sea-breeze of, 114 
China, 266, 470, 481-482 

coast-line of, 514 

famines in, 173 

Great Wall of, 495 
Chinook winds, 138 
Cincinnati, 422, 462, 569, 575, 597 
Circle of illumination, 18, 19 
Circulation of air, 112 
Cities, air of, 48 

on alluvial terraces, 377 

fogs of, 95 

increasing number and size of, 593 

location of, 593-601 

in tropics, 175 

types of, 595 
Civil War, campaigns at Vicksburg, 

369 

Confederate defenses along Missis- 
sippi, 370 

and Mississippi delta, 374 

sectionalism leading to, 549 

use of wind gaps in, 360 
Clays and clay products, 280, 565, 574, 

581 
Cleveland, 427, 429, 462, 577, 582, 597 
Cliff-dwellers, 355 
Cliffs, 522 

^Climate, affected by altitude, 120, 122, 
123, 198, 211, 504 

and cereals, 90, 193, 204, 205, 209 

changes of, 124 

chief factors of, 55 

as factor in life of plains, 491 

and manufacturing industries, 572 
Climates, of polar regions, 214-225 

of temperate zones, 178-213 

of tropical regions, 154-177 

of the U. S., 200-205 
Cloud-bursts, 149 
Cloudiness, 97, 162 



Clouds, 93, 95-97 

Coal, 48, 51, 280, 442, 466, 479, 570, 576 

conservation of, 282 

distribution of deposits, 281 

duration of supply in U. S., 281 

mining of, 281, 282 

total amount in U. S., 281 
Coal lands of Public Domain, 566 
Coastal plains, 489 

Atlantic, 272, 461, 492, 586 
Coast-lines and harbors, 514 

characteristics of, 515 

importance of, 514 
Cochabamba, 162 
Coke, 576 
Cold waves, 136 
Colorado Canyon, 354 
Colorado River, 426 

delta of, 372 
Columbia River, 426, 593 
Colidmbus, 23 
Comets, 8 
Commerce, of American seaports, 527 

difficulties of, in tropical countries, 
90, 92 

as influenced by form and size of 
earth, 12 

on the ocean, 226, 229, 514 

and trade- winds, 169 

of U. S. with other countries, 229 
Commercial cities, 595 
Conduction, 61 
Conglomerate, 259 

Connecticut Valley, influence on dis- 
tribution of population, 586 

mountains of, 310 

terrace-towns of, 377 
Continental climate, of temperate zones, 

195 

in U. S., 200-205 
Continental shelf, ^^, 34 
Continental winds, 117 
Continents, changes in areas of, 35, 294 

comparison of, 40 

grouping of, 35 

and ocean basins, ^^ 

and oceans, and temperature, 75 
Contour maps, 27 
Conservation, of coal, 282 

of forest resources, 559 

of ground waters, 328 

of iron, 286 

*of lakes, 403 

of lead, 287 

of mineral resources, 289, 442 



6o6 



INDEX 



Conservation — continued 

of petroleum, 284 

of soils, 268 

of waters in irrigation, 450 
Convection, 61 
Copper, 286, 479 

mines of Lake Superior region, 566 

produced in U. S., 565 
Coral reefs, 254 
Corn, climate for, 90, 193, 205 

distribution of, 209 

and frosts, 81 

production of, 537, 541 

water needed by, 50 
Corrasion, 338 

Cotton, 190, 492, 538, 547, 548 
Cotton gin, 548 
Cotton manufactures, 577, 578 
"Cow towns," 496, 497 
Crater Lake, 303 
Creep, 237 

of soils, etc., 333 
Crops, of chief importance in U. S., 
536, S4i 

grown in mountains, 475-476 

and marine climate, 193 

and rainfall, 118, 119, 124, 188, 209 

and relative humidity, 90 

rotation of, 47 

See Agriculture 
Crustal movements, 291 
Cumberland-Alleghany Plateau, soils 

of, 275 
Cumberland Gap, 360, 362 
Cumberland National Road, 359, 470 
Cycle of erosion, 352 
Cyclones, 128, 129, 130 

factors in climate, 196 

height of, 136 

movements of , 132, 135 

places of origin, 135 

and thunder-storms, 148 

tropical, 138-142, 168 

and weather, 136, 206 

of winter vs. summer, 136 
Cyclonic winds, 1 23 

Dairy products, 568, 576 
Danube River, 415 
Date palm, 373, 504 
Death Valley, 88, 90, 202 
Deeps, 233 

Deflection of winds, 128 
Degrees, length of, 18 
Delaware Water-Gap, 358 



Delta lakes, 375 

Delta, of Hwang-ho, 375 

of Mississippi, 374, 590 

of Nile, 375 
Deltas, 372 

and commerce, 518-519 

floods on, 375 

soil of, 375 
Denver, 599 
Deposition, by streams, 360-376 

by glacial waters, 407 

by glaciers, 394-399 

by ground-water, 331 

by waves, 523 

by wind, 314 
Desert conditions, human responses to, 

I7°-I7i, 501-507 
Deserts, 5, 499 

agriculture in, 501 

barriers to trade, 1 70 

commerce of, 505 

life in, 170, 499, 500 

political conditions in, 506 

of snow and ice, 507 
Detroit, 462, 580, 582 
Dew, 92, 93 

in tropics, 163 
Diastrophism, 291, 468 
Dikes, 3-10 
Distributaries, 374 
Distribution of population, 586 
Doldrums, 113 
Dover harbor, 532 
Drainage basin, 348 
Drift of ocean water, 243 
Drift, glacial, 265, 394 
Driftless area, 389 
Droughts, 124, 209 

and irrigation, 445 
Drowned valleys and harbors, 529 
Drowning of streams, 359 
Dry-farming, 99, 276, 496, 498 
Dry seasons, 159, 161 
Dry winds, 120 
Dunes, 314 
Dust of air, 50, 51, 313 

Earth, axis of, 12, 18 
form of, 10-11 
magnetism of, 29 
most favored of planets, 8 
motions of, 12 
orbit of, 13 
origin of, 8 
revolution of, 13 



INDEX 



607 



Earth — continued 

rotation of, 12, 13 

size of, 12 
Earthquakes, 294 

causes of, 296 

destruction by, 297 

distribution of, 295 

and movements of sea-water, 241, 
298 
Ecuador, people of, 486 
Elbe River, 415 
Equator, 12 
Equatorial calms, 113 
Equatorial climate, 160-163 

enervating to man, 164, 508 

and life, 163 
Equinoxes, 20 

Erie Canal, 433, 434,435, 470, 596 
Erosion, by glaciers, 391 

by ground-water, 330, ^^^ 

rate of, 339 

by rivers, 336-346 

by waves, 519-523 

by wind, 313-316 
Eskimos, 217, 222-224 
Europe, climate of northwestern, 77, 
191, 245 

commercial ports of, 516 

forestry in, 481 

general features of, 40 

trade with U. S., 229 
Evaporation, 85, 86, 88, 89 
Explorations, early, 23 

late, 24 

Fall Line, 417 
Falls, 356-358 

and rapids, and cities, 440, 597 
Farnuanimals, value of, 556 
Farm products, value of, 536 
Farm villages, 455 
Farming. See Agriculture 
Faulted mountains, 465 
Faulting, 296 
Ferries, and cities, 598 
Fertilizers, 575 
Figs, 373 
Fiords, 394 

as harbors, 530 
Fishing industries, 561-564 

of Arctic peoples, 507 

of British Isles, 254 

conditions favoring, 562 

of Labrador, 207 
Fissure eruptions, 308 



Flat boats, 420 

Flax, 549 _ 

Flood-plains, deposits on, 364 

soils of, 372 
Floods, 120, 211, 365, 375 
Florida, irrigation in, 458 
Flour and grist mill products, 575 
Foehn winds, 138 
Fog, 93 
Fogs, about icebergs, 242 

in London, 51 

over ocean currents, 246 

in polar regions, 218 
Food industries, 574 

of the sea, 254 
Forecasting of weather, 142 
Forest fires, 559-560 
Forest products, value of, 556 
Forest reserves, 455, 480 
Forest Service, 560, 579 
Forests, of equatorial regions, 164, 508 

evil effects of removal, 481, 482 

favored by humid climate, 194, 198 

in mountains, 480 

reclamation of sand areas by, 265, 
316 

reduce erosion, 269, 342 

repel settlers, 590 

of U. S., 556, 557 

conservation of, 559 
Frost, 78, 79, 81, 92, 188, 190, 209 
Fruits, in "frostless belts," 78 

in irrigated lands, 454 

preserving of, 567 

production of, in U. S., 550 

production of, near water bodies, 79 

in sub-tropical climates, 188 
Fur trade in mountains, 484 
Furniture, manufacture of, 440, 568 

Galveston, harbor of, 530, 531 

sea-wall, 141 

storm, 139 
Ganges River, 22, 413, 528 
Geography, definition of, 3 

divisions of, 3 

history of, 22 

relations of, 3, 4 
Geysers, 328 
Glacial deposits, 394-399 

and stream courses, 405 
Glacial epochs, cause of, 390 
Glacial erosion, 391-394 
Glacial period, 387 
Glacial soils, 275, 405 



6o8 



INDEX 



Glacial waters, deposits by, 407 

and early settlements in New Eng- 
land, 274 
Glaciers, 382 

effect on shore-lines, 517 

functions of, 382 

movement of, 385 

of Switzerland, 383, 384 

types of, 383 
Glass, 581 

Gloucester, 526, 562 
Gold, 286, 566 

in Black Hills, 590 

in California, 566 

production in U. S., 565 
Gorges, 354 

Grand Canyon of the Colorado, 354 
Granite, 259, 278, 568 
Grazing, 574 

in arid U. S., 202 

in the Great Plains, 203, 496, 553 

legislation concerning, 497 

on margins of deserts, 502 

in mountains, 476 

in public domain, 478 

in semi-arid plains, 494, 495 
Great Circle route, 18 
Great Lakes, cities on shores of, 597 

commerce of, 426-433 

coal trade of, 432 

development of steam navigation on, 
428 

early navigation of, 427 

freight rates on, 412 

grain trade of, 433 

history of, 403 

iron ore trade of, 431 

lumber trade of, 432 

navigation season on, 82, 380 

total shipments on, 427 
Great Plains, future use of, 498, 553 

history of, 495-498 

sand dunes of, 315 

soils of, 276 

underground waters of, 461 
Greenland, glaciers of, 219, 385 

settlements in, 222 
Ground- water, 321 

amount of, 321 

conservation of, 328 

courses followed by, 323 

importance of, 325 

movement of, 322, 324 

stored in alluvial fans, 364 

surface, 321, 322 



Ground- water — continued 

work of, 33°~333 
Guano, 194, 271 
Gulf of Mexico, 154, 533 
Gulf Stream, 243, 245, 246 
Gullies destroying land, 342 
Gypsum, 280 

Hail, 148 

Hammerfest, climate of, 216 

harbor of, 245 
Hanging valleys, 393 
Harbors, 514 

conditions determining value of, 525, 

595 

on Great Lakes, 427 

and ice, 82, 380, 381 

in rivers, 528, 529 

and tides, 247 
Hawaiian Islands, 122, 166, 302 
Hay, 454, 545, 547 
Health resorts, 80, 212, 600 
Heat of atmosphere, 55 

distributed by wind, in 
Heligoland, 522 
Hemp, 549 

High-pressure belts, in, 112 
Himalaya Mountains, and irrigation, 
1 19-120 

precipitation on southern slopes, 124 
Horses, 554 
Hot waves, 136 
Hudson River, 248, 417 
Hudson Valley, early population of, 
586 

and growth of New York City, 596 
Humid climate in temperate zone, 198 
Humid plains of low latitudes, 508 
Humid regions of U. S., 200, 203 
Humidity, 89, 162 

and air pressures, 109 

and crops, 90 
Humus, 257, 559 _ 

in equatorial soils, 164 
Hurricanes, 138-142, 168 
Hwang-ho River, 265, 375, 413 
Hydro-electric power, 441, 571 

Ice, on rivers, 380 

on seas and lakes, 380 

work of, 380 
Icebergs, 386 

dangerous to steamships, 242 
Igneous rocks, 259, 309 



INDEX 



609 



Igneous rocks — continued 

soils from, 264 

as water carriers, 461 
Illinois, glacial soils of, 405 

yield of corn throughout, 407 
Imperial Valley, 373, 448 
India, famines in, 173 

irrigation in, 445 

lava fields of, 308 

monsoons of, 115 

population of, 173 

rainfall in, 172 
Indiana, "boom" in gas field, 570 

glacial vs. non-glacial soils, 407 
Indians, of Arctic Coastal Plain, 507 

check expansion of whites, 588 

of Great Plains, 496 

of southern Appalachians, 474 

of Southwest, 502 
Indus River, 413 
Industries, location of, 567-573 

of the U. S., 535 
Inland waters and their uses, 412-464 
Inland Waterway, 359 
Insolation, 57, 59 
Intermediate zones. See Temperate 

zones 
Iron, 284 

distribution of deposits, 285 

estimated supply in U. S., 285 

in rocks and soils, 261 
Iron and steel industries, 574, 576 
Iron ore, importance of location, 566 

of Lake Superior region, 285, 431, 
479, 568, 576 

movement of, 432 
Irrigable land, area of, 449 
Irrigated land, crops of, 453 

not dependent directly on rain and 
snow, 119 

population capacity of, 455 

value of, 446 
Irrigation, 188, 277, 445 

from artesian wells, 327 

early practice of, in West, 445-446 

in Egypt, 445 

in Florida, 458 

government projects, 451-453 

in humid states, 456 

in India, 445 

in Indus Valley, 119 

and National Forests, 455 

in tropical regions, 165 
Islands, leading types of, in ocean, 34 
Isobaric gradient, 107 



Isobaric maps, 105, 108, no 
Isobaric surfaces, 106, 107 
Isobars, 104, 107, 128 
Isothermal maps, 70, 71, 73, 74 
Isotherms, courses of, 75 

Japan, climate of, 206 

earthquakes in, 298 

forest reserves of, 481 
Japan Current, 243, 246 
Java, population of, 155 

temperature of , 156, 160 
Jetties of the Mississippi, 338 

Kaffir corn, 545 

Kansas, settlement of, 497 

Kansas City, 423, 462, 497, 568, 575, 

597. 
Kaskaskia, 370, 600 
Kentucky, settlement of, 360, 588 
Krakatoa, 305, 307, 314 

Labrador, climate of, 206, 207 
Laccoliths, 309, 467 
Lake Agassiz, 401 

settlement of floor of, 402 
Lake Bonneville, 293 
Lake Chicago, 404 
Lake Iroquois, 405 
Lake-breezes, 114 
Lakes, on deltas, 375 

glacial, 392, 399 

oxbow, 369 

as sources of water supply, 461 
Land reduction, rate of, 341 
Land-breezes, 114 
Lands-, area and height of, S3 
Landslides, 297, 333 

and movements of sea- water, 241 
Latitude, 14 
Lava, 299 

intrusions of, 309 
Lava fields, of India, 308 

of the Northwest, 308 
Lead, 287, 590 

production in U. S., 565 
Leadville, Colo., 104, 479, 569 
Leather and its products, 574, 579 
Lemons, 188, 454 
Life, in Antarctic regions, 219 

in Arctic regions, 221, 222, 507 

in arid plains, 499 

in deserts, 170, 499, 500 

in the Great Plains, 495 

in humid plains of Low latitudes, 508 



6io 



INDEX 



Life — continued 

in mountains, 471-484 

in oases, 503 

in plains, 489-512 

in plateaus, 485-486 

in the sea, 252-255 

in semi-arid plains, 493 

in the temperate zones, 183 

in trade-wind zone, 169 

in well-watered plains of middle 
latitudes, 491 
Lightning, 148 
Limestone, 254, 259, 278 

soils from, 264, 273 
Liquors and beverages, 574, 580 
Littoral currents, 521 
Llanos, 165 
Load of streams, 338 
Loess, 265, 314 
London, air of, 49 

commerce helped by tides, 415 

fogs of, 51,95 
Longitude, 14, 15 

and time, 16 
Los Angeles, 462, 601 
Louisville, 423, 597 

tornado, 151 
Lumber and its products, 574, 578 
Lumber trade, of the Lakes, 432 

of Pittsburgh, 422 
Lumbering, 120, 556, 557 

kinds of wood cut, 558 

in Lake states, 432 

by states, 560 

Magnetism of earth, 29 
Malaria, in tropics, 164 

in U. S., 190, 460 
Malaspina Glacier, 386 
Manchester Ship Canal, 438 
Mantle rock, 257 
Manufacturing cities, 573, 599 

of New England, 570 
Manufacturing industries, 566-582 

of desert people, 502 

factors controlling location of, 567 

groups of, 574 

of interior river cities, 422-423 

of mountaineers, 484 

total value of products in U. S., 566 
Map projections, 24 
Marble, 279 
Marshes, and flow of streams, 401 

glacial, 397 

reclamation of, 273, 458 



Marine climate in high latitudes, 191 
Marine climates and crops, 193 
Marl, 400 

Mature topography, 350 
Mean annual temperature, 57 
Meanders of streams, 368 
Meat-packing industry, 497, 568, 574 
Mediterranean climate, 185 
Mercator's projection, 25 
Meridians, 14, 15 
Metal products, 574, 579 
Metamorphic rock, 260 

soils from, 264 
Meteors, 45 
Mexico, climate of, 68, 154 

people of, 486 

trade with U. S., 229 
Milch cows, 552, 553 
Millet, 545 

Milwaukee, 429, 462, 597 
Mineral fuels, 280 

Mineral industries, distribution of, 565 
Mineral plant foods, 270 
Mineral products, 278 

substitution for wood, 280 

of U.S., 565 
Mineral resources, conservation of, 289 
Mineral springs and waters, 329, 330, 

. 565 
Mining, 564 

in mountains, 478 
Mining cities, 479, 599 
Minneapolis, 440, 462, 575 
Missouri River, 419 

influence on distribution of popula- 
tion, 588 

transportation of sediment by, 266 
Mississippi River, 418, 419 

as a boundary, 419 

character of valley of, 345 

first improvements on, 365 

influence on distribution of popula- 
tion, 588 

traffic on, 426 

transportation of sediment by, 266, 
338 
Mohawk Valley, 417 

early population of, 586 
Moisture of atmosphere, 84-100 
Monadnocks, 351 
Monsoons, 115 

and trade on Indian Ocean, 116 
Monsoon climate, 1 71-173, 208 
Monsoon rains, 124, 168 
Montreal, 82, 596, 601 



INDEX 



611 



Moon, 7, 9 

and tides, 241, 248 
Moraines, 395, 396 

use of hilly, 275, 396 
Mosquitoes, 460 
Mt. Everest, 33 
Mt. Hood, 302 
Mountain breezes, 117 
Mountain climate, 159, 173, 210 
Mountaineers, industries of, 484 

life of, 471 
Mountains, 37, 465-485 

agriculture in, 474 

as barriers, 468 

destruction of, 467 

distribution of, 465 

effect on precipitation, 120, 122, 123, 

211, 504 

as forest reserves, 480 
life in, 473 
mining in, 478 
passes in, 470, 598 
as resorts, 212, 482 
settlement of, 474 
stock-raising in, 476 
types of, 465 

Nantucket harbor, 531 
Narrows, 358 
Nashville, 423, 597, 600 
National Forests, 455, 457, 482 

grazing in, 478 

lumbering in, 560 

to reclaim sandy areas, 265 
National Monuments, 483 
National Parks, 384, 483 
Natural gas, 284 

and glass making, 581 

in Indiana, 570 

produced in U. S., 565 

waste of, 47, 284 
Natural levees, 365 

and early population of Louisiana, 

367 
Navajo Indians, 502 
Naval stores, 492, 569 
Navigable streams of U. S., 416 
Navigation, 412-439 

affected by tides, 247 

on canals, 433~438 

cities on rivers at head of, 596 

of Great Lakes, 426-433 

of rivers, 413-426 
Neap tides, 251 
Nebulae, 8, 9 



Nebular hypothesis, 8 
Nevada, 473, 499, 590 
New England, early industries in, 274 

early population of, 586 

fisheries of, 254, 562 

manufacture of cotton in, 577 

manufacturing cities of, 570 

mountain resorts in, 483 

rivers of, 417 

soils of, 273 

use of water power in, 440, 441 
New Orleans, 240, 338, 374, 376, 423, 

S28 
New York harbor, 526, 532 
New York, 569, 571, 573, 599 

commercial leadership of, 526, 596 

and Erie Canal, 435 

location of, 601 

water supply of, 462 
New Zealand, 35, 178, 303 

geysers of, 328 
Niagara Falls, 441 
Nile River, 414 

delta of, 375 
Nitrate deposits, 194 
Nitrogen, 46, 47, 270 

in sea-water, 236 
Nomads, 494, 502 

North America, area and population in 
tropics, 154 

commerce of, 229 

general features of, 42 
North American ice-sheet. 388 
North Polar Zone, maps of, 215, 217 
North Temperate Zone, 179, 182 
Northers, 136 
Norway, agriculture in, 222 

climate of, 77 

coast of, 516 

emigration from, 475 

Oases, 503, 504, 505 
Oats, 539, 544, 546 

climate for, 193, 205 

distribution of, 209 
Ocean areas, 33, 228 
Ocean basins, ^^, 226 

and continents, ^^ 
Ocean currents, 241, 242-246 

and climate, 77, 245 

cold, 245 

equatorial, 243 

map of, 244 

warm, 245 

work of, 246 



6l2 



INDEX 



Ocean trade, 226 

and fogs, 95 
Oceans, 226-256 

area of, 33 

chief source of water vapor, 85 

depth of, 33, 233, 234 

exploration of, 230 

importance of , 226 

land areas tributary to several, 38 

life of, 252-255, 330 

materials of bottom, 230 

topography of bottom, 233 
Ohio, glaciated vs. unglaciated, 406 
Ohio River, 419, 426, 588 
Oil, See Petroleum 

used to diminish storm-waves, 241 
Old topography, 350 
Omaha, 462, 497 
Oozes, 232 

Oranges, 188, 190, 454 
Oregon Trail, 471 

Ores, 331,479 

mined in U. S., 565 
Out wash plain, 408 
Oxygen, of the air, 46, 47 

in sea-water, 236 

in soils, 270 
Oyster fisheries, 562, 563 
Ozone, 46, 50 

Pacific coast fisheries, 563 

Packing industry, 497, 568, 574 

Panama Canal, 169, 439, 533 

Paper and printing, 574, 579 

Para, 529 

Parallels, 14 

Pastoral tribes, 165, 494 

Peary, R. E. F 24 

Peat, 283 

Pelee, 301, 306 

Peneplains, 351 

Penguins, 219 

Peoria, 425, 580 

Perihelion, 13 

Peru, people of, 486 

Petrified wood, 332 

Petroleum, 283 

produced in U. S., 565 
Philadelphia, 462, 569, 573, 575, 576, 

578, 596, 599, 600 
Phosphates, 271 

produced in U. S., 565 
Piedmont alluvial plain, 363 
Piedmont glaciers, 386 
Piedmont Plateau, 37, 575 



Piedmont Plateau — continued 

early population of, 586 

soils of, 275 
Pig iron produced in U. S., 565 
Piracy of streams, 360 
Pittsburgh, 422, 426, 576, 597 
Plains, 36 

advantages of, 489 

classes of, 489 

contrasts among, 491 

density of population in, 490 

life of, 489-512 
Planetesimal hypothesis, 9 
Planets, 7, 8 . 
Plant life, and ancient ice-sheets, 409 

of Antarctic regions, 219 

of Arctic regions, 221, 507 

dependence on ground- water, 3 24 

in deserts, 499 

on mountain slopes, 476 

in the sea, 252-254 

and soil formation, 262 

and water vapor of air, 85 
Plateaus, 36, 485-486 
Pleasure resorts, 114, 600 
Polar regions, climate of, 214-224 

extent of, 214 

land and water areas in, 214 
Poles, seasons at, 67 
Pompeii, 305, 307 
Population, distribution of, 325, 586-600 

engaged in agriculture, 535 

factors affecting density, 586 

maps, 587, 589, 592, 594, 595 

and rainfall, 119 

rural vs. urban, 593 

of the tropics, 155, 175 

at various altitudes, 490 
Pork-packing, 575 
Portland cement, 278, 280 
Potassium, in soil, 270, 271 
Potatoes, 550, 551 

Pottery, manufacture of , by Indians, 502 
Poultry and eggs, 556 
Prairies, 276 

settlement of, 590 
Precipitation, 86, 98 ' 

and altitude, 211 

in California, 122 

and density of population, 593 

factors determining, 120 

on mountains, 123 

in trade- wind zone, 1 20 

in U. S., 122, 197 

for the world, 121 



k 



INDEX 



613 



Pressure of air, and altitude, 103 

and boiling, 104 

distribution of, 104 

effects on man, 176 
Projection, conical, 26 
Pygmies, 511 
Pyrenees, 468 

people of western valleys, 474 

Quarrying, 564 

Quebec, 601 

Quito, temperature of, 160 

Radiation, 60 

Railroads, accidents on, and fogs, 95 

and cattle industry, 496 

competition with waterways, 425 

development of, 590 

freight rates, 412 

and growth of cities, 598 

problems of, in deserts, 1 70 

problems of, in equatorial regions, 
164 

projected across Sahara, 506 

and snowslides, 212 

and standard time, 17 

transcontinental routes, 227 

of the U. S., 591 
Rain, 84 

how disposed of, 321 

rate of fall and value, 1 20 
Rainbow, 148 

Rainfall, affected by altitude, 120, 122, 
123, 211, 504 

and agriculture, 118, 119, 124, 188, 
209 

annual, of world, 123 

distribution of, 120 

on lee coasts, temperate zone, 188, 
208 

of .marine climates, 192 

of the Mississippi Basin, 123, 132 

in trade-wind zone, 166, 167, 168 

in tropical zone, 158 

of the U. S., 197, 199 

variation in, 124 

and winds, 118, 120 

in zone of westerly winds, 122 
Rain-making, 99 
Rainy seasons, 159, 161 
Rapids, 356 
Reclamation, cost of, 452, 459 

of lake lands, 400, 460 

of swamp lands, 458 
Reclamation Service, 449, 455 



Red clay, 232 
Red Sea, 239 
Reefs, 523 

coral, 254 
Refrigerator cars, 455, 550 
Reindeer, 507 

Rejuvenation of streams, 360 
Relief features, ^3 
Relief maps, 27 
Rhine River, 4, 415, 514 

Valley, 471 
Rhone River, 415, 528 

Valley, 471 
Rice, 190, 545, 547 
River cities, 165, 422, 596, 597 
River navigation, 413-426 

decline of, 425 

development of, 420 

present traffic, 426 
River system, 347, 348 
River valleys and human life, 340 
Rivers, as boundaries, 371 

of foreign countries, 413-416 

ice of, 380 

and shore-lines, 518 

tides in, 248 

of U. S., 416-426 
Rock waste, 257 
Rocky Mountains, as barriers, 471 

early settlements in, 590 

fur trade in, 484 

and precipitation, 123 

soils in, 276 

sparsely settled, 474 
Roosevelt dam, 453 
Rye, 69, 545 

climate for, 90, 193 

distribution of, 209 

Sahara, 90, 122^167, 169, 170, 315, 503, 

504, 505, S°6, 507 
St. Louis, 72, 423, 484, 407, 573, 597 

tornado at, 151 
St. Pierre, 307-308 
Salmon industry, 563, 568 
Salt, 92, 288 

deposits of, 202 

and early settlement of Interior, 288 

produced in U. S., 565 

of sea, 235, 236, 330 
Salton Sea, 86, 373 
San Francisco, 72, 596 

earthquake at, 298 
San Francisco Mountains, 123, 301 
Sand, abrasion by, 314 



614 



INDEX 



Sand — continued 

for making glass, 581 
Sand bars, and navigation, 364 
Sandstone, 259, 280 

soils from, 264, 273 

as water bearer, 461 
Satellites, 7 
Saturation of air, 89 
Sea, ice of, 381 

topography of bottom, 233 

See Oceans 
Sea-breezes, 114 
Sea-island cotton, 548 
Sea-level, changes of, 291, 292, 293 
Sea-water, color of, 237 

composition of, 235 

gases in, 236 

movements of, 237, 239, 240, 241, 305 

temperature of, 238, 239 
Seal fisheries, 222, 254, 564 
Seasons, 64-67 

in high latitudes, 66 

in low latitudes, 66 

in middle latitudes, 64, 183 
Sediment, amount carried to sea, 338 

how carried, 231, 337 

of the sea-bottom, 230-232 
Sedimentary rocks, 259 
Seismograph, 294 
Semi-arid climate in temperate zone, 

198 
Semi-arid regions, 200, 202 

life in, 203, 493-498 
Sensible temperature, 88, 157 
Shackleton expedition, 216 
Shale, 259 

soils from, 264 

as water bearer, 461 
Sheep, 554 

Shenandoah Valley, 474 
Shipbuilding, 574, 581 
Shooting stars, 45 
Shore-lines, and harbors, 514-533 

modification of, 517 
Sidereal day, 1 2 
Sierra Nevada Mountains, climatic 

barriers, 122, 191, 200, 473 
Silk manufacture, 569, 578 
Sills, 310 
Silver, 287, 590 

production in U. S., 565 
Simoons, 313 
Sirocco, 136 
Slates, 280 
Slavery, in Alabama, 492 



Slavery — continued 

and cotton culture. 548 

favored by climate of South, 190, 273 
Slumping,_333 
Snoqualmie Falls, 442 
Snow, 380 

fields, 382 

flakes, 92 

and temperature of air, 70 

value of, 81, 120 
Snowfall and altitude, 211 
Snowslides, damage by, 212 
Soil, 257, 260-272 

alkaline, 119 

of arid regions, 202, 448 

character influenced by rainfall, 119 

classes of, 264 

conservation of, 268 

and dew, 93 

evils resulting from erosion of, 267 

factors determining fertility, 271 

and frost, 79 

importance to man, 260 

making of, 261 

plant foods in, 270 

produced from volcanic materials, 301 

provinces in U. S., 272-278 

waste of, 267 
Solar day, 12, 13 
Solar System, 7 
Solstices, 14, 20, 59 
Soo Canal, 429 

South America, area and population in 
temperate zone, 178 

area and population in tropics, 154 

distribution of population in, 174 

general features of, 41 

trade with U. S., 229 
South Pass, 471 

South Temperate Zone, 178, 182 
Spanish Trail, 353 
Spits, 524, 531 
Spring tides, 251 
Springs, 325, 326, 328, 329 
St. Anthony's Falls, 440 
Steamboat trade on Mississippi, centers 

of, 422 
Steamboats, 420, 428, 433, 514 

losses of, 364 
Steamship routes, 227 

vary with seasons, 242 
Stock-raising, in mountains, 476 

in the early western settlements, 419 

on the Great Plains, 496 
Storms, 126, 128 



r 



INDEX 



6i5 



Storms — continued 

destruction by, 139, 142 
Stratified rocks, 259 
Streams, accidents to, 359 

as boundaries, 371 

deposition by, 360 

meanders of, 368 

as sources of water supply, 462 

work of, 336 
Submerged valleys, 235 
Subsoil, 259 
Subtropical climates, 185-187 

crops of, 188 
Sudan, 165, 170, 503 
Suez Canal, 430, 533 
Sugar, 552, 571 
Sugar-beet, 454, 552 
Sugar-cane, 190 
Sugar plants, 552 
Sun, apparent motion of, 21 

heat of, as source of power, 98 

nature and origin of, 8, 9, 10 

source of heat of atmosphere, 55 

and tides, 241, 250 

worship of, 171 
Sunshine, hours of in U. S., 97, 98 

Sunstrokes, 136, 157- 

Swamps, reclamation of, 273, 458 
Swine, 554 

Switzerland, disadvantages of inland 
location, 514 

glaciers of, 384 

Talus, 262 

Tanning industry, 580 
Temperate zone, northern, seasons in, 
183 

temperature range in, 181 
Temperate zones, area of land in. 178, 
179 

climate of , 178-212 

extent of, 178 

population of, 1 79 
Temperature, and air pressure, 109 

and altitude, 67 

changes and rock-splitting, 261, 262 

daily range in deserts, 80 

distribution of, 60 

and evaporation, 88 

of land and water, 63, 75 

mean maximum, 57 

mean minimum, 57 

range of, 72, 78, 80, 81 

in temperate zones, 195 

in tropical zone, 156 



Tennessee, settlement of, 588 
Terraces, alluvial, 376 

of drift, 408 
Terracing, for agriculture, 269, 475 
Texas, cattle industry of, 496 
Textile manufactures, 92, 574, 577, 

578 
Thermal equator, 75 
Thermometers, 55, 56, 79 
Thunder-storms, 147, 148 

and cyclones, 148 
Tidal water power, 252 
Tides, 241, 246-252 
Till, 394 
Timber-line, 210 
Tobacco, 550 

Tobacco products, 574, 581 
Tornadoes, 128, 149 
Trade-wind climate, 122, 159, 166, 167 

and life, 169 
Trade-winds and commerce, 169 
Tree-line, 476 
Tropical climate, 154-177 

characteristics of, 156 

and disease, 164 

and life, 165 

types of, 159, 161 
Tropical forests, animals of, 509 

commerce of, 512 

life in, 508 
Tropical regions, area of land in, 155 

climate of, 154-176 

extent of, 154 

natives of , 157, 158, 164, 508-512 

population of , 155, 175 
Tropics, of Cancer and Capricorn, 21, 
22 

future of, 176 
Truckee Pass, 471 
Tundras, 507 
Turpentine, 569, 579 
Typhoid fever, 462 
Typhoons, 142 

United States Department of Agricul- 
ture, 541 

Valley breezes, 117 

Valley system, 347, 348 

Valley trains, 408 

Valleys, as centers of human activity, 

340 
growth of, 342-346 
stages in history of, 34S 
Vegetables, canning of, 567 



6i6 



INDEX 



Vegetation, of Antarctic region, 219 

of Arctic region, 221 

in deserts, 499, 500, 502 

in high latitudes, 67 

on mountain slopes, 69, 123, 476 

of oases, 504 

in the tropics, 164, 175 

See Plant Life 
Veins, 331,479 
Vicksburg, 369, 597 
Volcanic cones, 235, 302, 466 

destruction of, 303 
Volcanic plugs, 304 
Volcanoes, 299-308 

destructiveness of, 305 

distribution of, 301 

number of, 301 

products of, 299 

in sea, 235, 241, 301 
Volga River, 414 
Vulcanism. 299 

causes of, 310 

Washington, D. C, 600 
Water power, 440-444 

afforded by hanging valleys, 393 

amount developed, 441 

control of, 443 

distribution in U. S., 442 

furnished by mountain streams, 444, 

48S 

furnished by tides, 252 

future importance, 441 

and manufacturing, 569 

in other countries, 444 

of Ottawa Valley, 427 
Water supply, 461 
Water table, 321 
Water-gaps, 358 
Water vapor, 46, 50 

circulation of, 85 

sources of, 85 
Waterspouts, 151 
Wave-cut terraces, 522 
Waves and wave action, 241, 519, 520, 

S2i, 523 
Weather Bureau, 80, 118, 126, 144 

value of work of, 146 
Weather forecasting, 126, 142 



Weather lore, 144 
Weather maps, 126 

interpretation of, 128 
Weathering, 261 
Wells, artesian, 326 

and domestic water supply, 461 

and irrigation, 458 

pollution of waters of, 324 
West Indies, cyclones of, 138, 139, 142 
Westerly winds, rainfall in zone of, 122 
Whaling industry, 169, 222, 254, 563 
Wheat, 188, 540, 543, 544, 545 

climate for, 90, 193, 204, 205 

distribution of, 207, 209 
Whirlwinds, 148 
Whiskey, 419, 580 

Wills Creek, narrows of, 359, 588, 599 
Wind, 102, in 

velocity of , 107, 118, 129, 132, 135 

work of, 313, 314 
Wind zones, 112 
Wind-gaps, 360 • 
Winds, 106, 107, 128 

causes of , 106, in, 113 

deflection of, 128 

and distribution of temperature, 76, 
in 

easterly, 113 

importance of, in 

and movements of sea-water, 241 

oceanic, 117 

periodic, 113 

planetary, 113 

prevailing, 113 

and rainfall, 118, 120 

trades, 113 

westerlies, 113 
Wine, manufacture of, 568, 580 
Wood-pulp, 441, 568 
Wood-working industries, 568 
Wool clip of U. S., 554 ■ 
Woolen manufactures, 578 

Yang-tze River, 413 
Yellow fever, 164, 190 
Youthful topography, 350 

Zinc, 287 

produced in U. S., 565 



iP OF NORTH AMERICA. 



Plate I. 





<j> 100 200 300 400 50 ^ | V 

English Statute Miles 

I 



100 Longitude 



ITED STATES. 




¥ 









Jf 






^^klf^ 



i 

Omaha 






I>ul)uqTiec 

<5\ W A 

)Des Moines^ 



P 



T?eoria \4&/ 






sCity 

Jeffei 
C 

M 

Joplin 



')l il L IN 1 Sfloi' BauteU / ctaciD ^ti r 



City <&V* \l Evansynhe^^^ouii^V^ \ 1<" XTV" P^&§!ov 

MISSOURI]^ /TStn-*-*! £ S^Ov^iA pT^&i^ — ;"&, 

aplto 
ARKANSAS 




K. 



Silr 



CsNashvUJL 
T ElN NESSf 



^s£rU)«/ 



Raleigh 
NOBTHS\C A, S 



JHot Spflngs V^A -n ! BiIffliBgr ^ , l^ A>lanta ^^r 

4— (*. =y \i / vr \ ^\ 

j )" MMIf5ISSTPPl\ ALABAMA '. . 

1 Jb Wackson | / /^ Montgc 
.^XVicksburg ! ( ' 



PHYSICAL MAP OI 




TH AMERICA. 



PLATE III. 




OF EUROPE. 



Plate IV. 




~25 30 ~35 " 40 4$ >l 5\ 



.y^^i jg e I ^ 



PHYSICAL MA 



30 40 50 CO 7 70 C 




EXPLANATION OF COLORS 

Above C000 feet 

3000 to 0000 feet 

1500 to 3000 feet 

600 to 1500 feet 

Sea Level to 600 feet 

Depression below Sea Level 

Sea depths below 100 fathoms 
colored in darker blue 



£ ATLAS. LONrO'- : MEIKLEJOHN AND MOLTEN 



■tiering Strait 



)F ASIA. 




[CAL MAP OF AFRICA. 



Plate VI. 
















C.L ee M 



EXPLANATION OF COLORS 

1 

Above 6000 feet 

3000 to 6000 feet 

1500 to 3000 feet 

600 to 1500 feet 

Sea Level to 600 feet 



1= Depression below Sea Level 

Sea depths below 100 fathoms 
colored in darker blue 




100 200 300 400 600 60 

English Statute Miles 



130 Longitude 



East 140 froT 



KLEJOHN ANC -iOlDEV 



3F AUSTRALIA. 



Plate VII. 




